I have taken the synopses from wikipedia and Conan The Movie Blog.
Everything that is described by Howard is in blue , though it might be altered substantially.
Everything in green is a Howard name taken out of context, such as from a non-Conan story.
Everything in orange is an event from a Howard story taken out of context. Some examples may be from Conan stories, others from non-Conan Howard stories. Those that are taken from non-Howard Conans (such as De Camp's "The Thing in the Crypt") are not under scrutiny, because I don't care about those elements.
Anything in red text denotes something not just absent in the Howard stories, but antithetical to Howard's themes. This is some of the more egregious stuff, like the entire backstory, Conan praying to Crom, the Hyborian Age being quasi-Bronze Age, as well as a few others. Basically, if I can't see it happening in a Howard story due to it being out of character or outright impossible, it's going to be in red. I've no doubt this will be particularly controversial, so I invite people to debate whether something I consider "anti-Howard" or "un-Howard" is valid. I'll be providing annotations for further discussion.
Anything in plain text is a complete invention of Oliver Stone and John Milius, or Thomas Dean Donnelly & Joshua Oppenheimer in the case of the upcoming film.
Then, compare the amount of bold & italics to the plain text. That should give you an idea.
A yet-unseen Wizard (Mako) narrates the story, with an altered version of the Nemedian Chronicles. As a young Cimmerian boy, Conan witnesses the destruction of his village at the hand of three Vanir warlords: Thulsa Doom (James Earl Jones) and Doom's lieutenants, Rexor (Ben Davidson) and Thorgrim (Sven-Ole Thorsen). They are led there by a Pict. Conan's father, a blacksmith (William Smith) valiantly fights the bandits, but Thorgrim and Rexor mortally wound him, finally killing him with their pack of trained dogs. Doom himself hypnotizes and then decapitates Conan's mother. The battle standard carried by the invading Vanir - two snakes facing each other over a moon and a rising sun - is burned into the memory of young Conan.
Sold into slavery along with the other children from his village, Conan is forced with others to push a human-powered mill, The Wheel of Pain. Reaching adulthood as the sole survivor, he has become broad and strong, (at this point the viewer is introduced to an adult Conan via the massive back and stoic stare of a 33-year-old Arnold Schwarzenegger). After a period of enduring the elements, a lone horseman appears. Conan, it appears, is purchased on the premise that size alone is good enough to qualify him to fight as a gladiator. After success competing in the gladiator arena, as Akiro describes, Conan discovers his own worth. His owner sees such potential in Conan that he is later taken to the Far East. There Conan is trained as a swordsman by "War Masters." While still a slave, Conan studies language and writing including poetry and philosophy. After many successful fights, his owner spontaneously sets him free. After discovering a sword from an ancient Atlantean king in a tomb, Conan dedicates his life to vengeance. He meets with a witch, who tells him to go to Zamora, and during an unholy union she goes a bit demonic.
During his travels, Conan meets two thieves: Subotai (Gerry Lopez), a Hyrkanian archer; and Valeria (Sandahl Bergman). The trio learn that a doomsday cult dedicated to Set has arisen in the past few years, one which makes extensive use of snake symbolism. Conan punches a camel at some point, high on black lotus. While breaking into one of the cult's fortified temples in Shadizar, Conan discovers Rexor overseeing a human sacrifice, a confirmation of the cult's connection to Thulsa Doom. The thieves succeed in making off with (among other things) a large jewel famously dubbed "The Eye of the Serpent," and a jade amulet in the shape of Thulsa Doom's Vanir battle standard; the emblem of the Snake-god Set. In the process, Conan and his fellow thieves are forced to kill Thorgrim's pet, a giant snake guarding the treasure.
As the three enjoy their stolen wealth, Valeria becomes Conan's lover. The wealth is their undoing; drunk with excess, Conan and his companions are captured by soldiers of King Osric of Ophir (Max von Sydow). Initially appearing enraged, he then reveals his respect for their exploit in challenging the snake cult, and offers them a fortune to return his daughter (Valérie Quennessen), who has been seduced into joining the cult. He shows them a dagger, the "Fangs of the Serpent", with which a father was killed by his cultist son by plunging it into his heart, and fears a similar fate awaits him.
Valeria's expressed desire is to settle down, so Conan makes off on his own in the night, without Valeria knowing, pursuing his family's killer to Set's Mountain of Power. He happens upon the Wizard Akiro (the story's narrator). Akiro is a recluse who watches over the Mounds: a haunted Stonehenge-like cemetery. Conan is respectful of the Wizard's status, and the two become friends almost immediately.
Arriving at the Mountain of Power, Conan mugs a priest for his robes and uses the snake-amulet he stole from Rexor's tower in Shadizar as a pass to reach the head of the worshippers. However, a guard becomes suspicious and shows it to Thorgrim and Rexor. Conan is captured, beaten and brought before Thulsa Doom. He explains that in his youth he was searching for steel. Doom tells Conan the "Riddle of Steel": "Steel isn't strong: flesh is stronger." To prove his point, Thulsa Doom bids one of his followers - a beautiful young girl - to jump from a high ledge to her death, which she promptly does. Doom charges that his flesh, as a weapon, is much more potent than any sword. Doom orders that Conan be crucified in the desert, on the Tree of Woe. Here, he bites the neck of a vulture which attempts to peck at him.
Conan is found by Valeria and Subotai, near death. They bring him to Akiro, whom Valeria orders to revive Conan. In response to his technique, Akiro tells Valeria that the Gods of the Mounds will exact a terrible price on whoever asks for such. Valeria tells him that she "will pay them!" Akiro's spells ward away spirits to ensure Conan's survival. As Conan's broken body heals, Valeria tells him that - if need be - she will rise against death itself to fight by his side.
Conan and his fellow adventurers enter the Mountain of Power to rescue King Osric's daughter where they witness the cults' orgy: a bizarre feast, at which the cult members dine upon a green stew consisting of human body parts. Thulsa Doom at this point transforms into a giant snake. The thieves battle Thulsa Doom's guards, who are led by Rexor and Thorgrim. They sweep into Doom's orgy room, scatter the snake-lord's harem and grab the princess. Valeria is mortally wounded during the escape when Thulsa Doom shoots her with an arrow created from a venomous snake. She dies in Conan's arms. Conan brings Valeria back to the Mounds. Despite Akiro's claims that no fire will burn here, Conan cremates his lover on a funeral pyre.
Before the approaching battle, Conan prays to Crom to help him gain revenge against Doom's warriors. Thulsa Doom, Rexor and Thorgrim lead their small army of "Vanir" riders to recover Osric's daughter. The Vanir are killed one by one and Thorgrim is killed by a clever trap. Rexor, angered at his friend's death, charges at Conan, almost catching him by surprise. The two engage in a fierce battle with Conan on the defensive. Rexor gains the upper hand and just as his sword is about to slay Conan, it is then blocked by the heavenly sword of Valeria, who quickly strikes him in the face. Making good on her vow to return should Conan ever need her she says to him "Do you want to live forever?" and vanishes.
As Rexor recovers from the blow, he resumes his attack on Conan. Conan parries his blows easily, cleaving through the sword that Rexor stole from Conan's father and kills him. Thulsa Doom, the battle lost, attempts to kill the princess with another enchanted snake-arrow, but it is deflected by Subotai's leaping shield. The princess calls out for her father and Doom's spell over Osric's daughter is broken at last. Conan, staring at his fathers broken sword, realizes the meaning of the Riddle of Steel.
Later at night, a torch-bearing Thulsa Doom preaches to his cult members, who also bear torches: the gleam in the eye of Set, as it were. Conan, led by Osric's daughter, kills a cult sentry, then emerges from the shadows behind Doom. The snake-lord attempts to hypnotize the barbarian, as he hypnotized Conan's mother years ago. But Conan is too strong-willed for him; he beheads Doom with his father's broken sword. The barbarian casts Doom's head from the temple balcony, down the steps leading up the Mountain of Power. The severed head of their leader comes to rest at the feet of Set's followers... along with the broken sword of Conan's father. The awakened "Orphans of Doom" drop their torches into a ceremonial fountain at the base of the Mountain, then vanish into the darkness for home. Conan takes a hanging fire and throws it at the Mountain of Power igniting it. By dawn the fire has engulfed it as Conan carries the princess home.
The film's epilogue shows an aged Conan sitting upon a throne, crowned as King. A narration by Akiro tells the epilogue of the tale. In an alternate DVD release of the film, the final line, both written on screen and spoken by Akiro is "... in time, he became a king by his own hand... [and] this story shall also be told."
Now let's look at Doppenheimer's masterpiece. Anything in italics is a detail I added from the casting sheet.
icy fields of Cimmeria, a child is born, cut out of his mother’s womb by his father, CORIN. With her last breath, she names him CONAN. Caucasian, tough and wiry, scary violent. At ten, he insists on joining the teenage boys entering their rites into becoming warriors. When four Picts cross his path and kill one of the boys, Conan unleashes a savagery that goes too far for a warrior. His father takes him aside and personally trains him. His father teaches him what makes a good sword but he has still much to learn what makes a good swordsman. The young boy quickly proves himself an innate if impulsive warrior. The young warrior is inquisitive about the outside world, and while his father tries to shield him, in time the world comes to their doorstep. He's in his 30s to 40s, Caucasian, powerfully built, intelligent, graceful, master swordsman, skilled blacksmith, de facto leader of Cimmerians and Conan's father. He resolves to answer the terrible request of his dying wife and cuts Conan out of her so she can see him. He then shoulders the burden of raising Conan, which proves to be daunting given the boy's savage nature. Corin teaches his son the meaning of the sword: a hot blade must be cooled and tempered.
KHALAR SINGH, a powerful warlord, arrives with his band of mercenaries, demanding not gold or steel, but one woman from each bloodline. He is driven in his quest to find the Queen of Acheron and has been building an empire to do so. His goal is to find the Queen whose blood will bring life to the demonic minions of Acheron while making himself king of this hellish power. With this power, Khalar will protect his legacy against the onslaught of master sorcerer, Thoth-Amon so that his weak son, Fariq may rule after his death. The Cimmerians refuse and a massive battle ensues. Khalar Singh winning the day through the use of black magic. Corin, knowing the battle is lost, hides Conan, at the cost of his own life. When Khalar finally corners him and tortures him to death, he shows no regret nor pain, hiding his concern for his son's safety from the eyes of the enemy. Conan, wracked by the guilt of a survivor, vows his revenge on Khalar and his warriors. When we meet Conan again, many years later, he’s grown into a powerful and experienced warrior. He is a savage killer that has matured into the refinement his father tried to teach him when he was young. His entire life, from the moment of his birth, has been shaped by violence. Being the last of his tribe and having to watch his father die a cruel death, he is determined avenge his peoples slaughter by killing all those who led the attack on the Cimmerians, including the all-powerful Khalar Singh. He is prepared to die in order to accomplish his goal. What Conan did not expect, was to find a reason to live….
His revenge is nearly complete as he traps one of the few of Khalar`s former warriors still left alive. LUCIUS. He's in his 30s, Caucasian, handsome, proud, haughty, lethal, a leader of a Legion of Aquilonian Mercenaries. While attacking Corin and Conan in close quarters, he is thrown into a fiery forge that disfigures him for life. His self-revulsion twists him to the point that years later he takes great pleasure in torturing prisoners. Before killing him, Conan discovers Khalar’s location in the distant Khauran. In a hidden oasis in the desert, Khalar finds TAMARA, the last of an ancient royal line, the one person he’s been searching for the past twenty years. She is 18 to 24 years old, Caucasian or Middle Eastern, open to all ethnicities; beautiful, studious, correct, a novitiate of a Greek influenced monastery. A master of martial arts, she has been trained to be the Queen's servant, bodyguard and best friend. She and many other female bodyguards to the queen have been in hiding most of their lives because of the curse of Acheron, which would take the queen's life to bring almost immortal power to its king. She finds herself in league with Conan because of a mutual need to find Khalar Singh.
Tamara, unknowing of her own identity, is told to flee by her mentor, FASSIR, even as Khalar’s forces enslave or massacre the oasis’ people. Tamara escapes, and a furious Khalar sends his men scouring the countryside for her. She is separated from Ilira, the one she must protect. With all of her strength and will, Tamara is determined to find and rescue her. But her path crosses Conan’s first, and instead of setting her free he decides to use her as bait to draw Khalar out from behind his protective shield of warriors. But the plan fails and Conan and Tamara must work together to escape, an escape which first reveals a great power building inside the frightened girl. She is not in the least intimidated by Conan's size or grim demeanor and their alliance eventually blossoms into something that surprises them both.
Conan ends up on a pirate ship that Tamara’s people have commissioned to take her far from Khalar‘s grasp. (Led by Artus) He's in his 30s, tan and swarthy, almost Gypsy-like, handsome, charming, even dashing in a gruff way, a Zamoran pirate and good friend to Conan. They have shared many adventures together and trust each other with their lives. Artus is a master of the high seas with a fast and powerful ship. He shows his mastery in strategy and hand-to-hand combat during a fierce sea battle. Conan learns of Khalar’s plan: to revive the ancient and evil empire of Acheron by sacrificing the only living heir to its throne, Tamara. Simura explains that Khalar desires the power, which now grows inside Tamara, a power, if unleashed, would once again bring all mankind under Acheron’s bloody and brutal reign. The truth of her destiny has been hidden from Tamara, for her own good, but when the treacherous pirates try to turn her over to Khalar’s forces, even Conan’s brute force is little compared to the explosion of energy unwittingly released by Tamara. In the smoldering aftermath, only Conan and Tamara are left alive.
Conan tries parting ways with Tamara, intent on his own revenge but she asks him for help getting into Khalar’s forces to rescue her people. Like Conan, Tamara can bear no more blood on her hands. Conan finally relents and they make love, not knowing that Khalar is performing a ritual, sacrificing part of his soul to create a demon to help him kill Conan. Once inside the fortress. Conan kills the massive JAILER, and Tamara finds many of her people, including Fassir, still alive. Fassir reveals he’s a traitor, turning Tamara over to her enemy. Conan falls into Khalar`s trap, forced to battle the demon he summoned. THE SHADOW OF NERGAL. Conan survives, then forces Fassir’s acolyte, BAEL, to lead him to Acheron, where Tamara is to be sacrificed. The ghosts of the ancient ruins of Acheron come alive as the last of the royal line, Tamara, is led up to the sacrificial altar. Conan arrives and starts cutting a swath through the soldiers that block his path to her, including his main revenge target, UKAFA. Conan finds Khalar to be a tough opponent. As Tamara is about to be killed, her eyes tum black and she fully assumes the form of Queen of Acheron, and unleashes her power. After Conan kills Khalar, Tamara begs him to kill her too. so the power within her won`t rise to shed more blood. Conan reluctantly agrees and plunges a spear into her chest. They share one last kiss as she dies in his arms.
So. There you go. A surface analysis would indicate that Conan the Barbarian has more Howardian elements than "Conan," while the latter has slightly more "anti-Howardian" elements. Conan the Barbarian has a few elements taken out of context from Howard stories, while "Conan" has practically none. However, the Howard elements that are present poison the well for future adaptations, especially "A Witch Shall Be Born," "The Tower of the Elephant," and "Queen of the Black Coast," which spoils any good will I have towards those factors.
When it comes to the central character, both "Conans" are equally wretched, in my mind. 1982 "Conan" is the antithesis of Howard's: enslaved instead of free, domesticated instead of independent, educated as opposed to learned, illiterate and monosyllabic instead of polyglot and talkative, clumsy and slow instead of swift and deadly. 2010 "Conan" may not have been enslaved and grows up a barbarian, but he's no less a slave to his childhood trauma: his entire life is dedicated to vengeance, he's haunted by the ghosts of his past (quite literally, going by the most recent draft), he laments the blood spilt in his name. He's a damaged, troubled boy who's never let go of his broken childhood.
Supporting cast is a similar conundrum to the other Howard elements. The use of Thulsa Doom and Valeria means that "The Cat and the Skull" and "Red Nails" suffer from comparison to their Conan the Barbarian counterparts, not to mention the iconic vulture moment anticipating "A Witch Shall Be Born." At least Khalar Singh, Tamara and the like don't ruin real Howard character's chances. Still, the complete ruination of Howard's Hyborian Age (how can Singh muster an army without running into Aquilonia, Nemedia, Hyperborea or any of the other nations? Since when did Khauran have need for warships? How can the nonsense about Acheron possibly be reconciled with The Hour of the Dragon?) balances it all out.
So all things considered, it truly depresses me to say that Conan the Barbarian does have more Howard in it than this miserable mess--however, by virtue of diluting, misappropriating and subverting those same elements, the end result isn't much better. The only way I can see Conan the Barbarian being superior to "Conan" is on pure cinematic quality, and frankly, I don't think Milius has anything to worry about on that front.