I'm generally of the opinion that D&D's primary inspirations were literary rather than cinematic. Nevertheless, there are a handful of films that can genuinely claim to have been inspirations for the game and, though released in 1973, I think a good argument can be made that The Golden Voyage of Sinbad is one of those movies -- or, if it isn't, it's very much in line with the kind of fantasy films we know Arneson and Gygax watched and enjoyed. Like its 1958 predecessor, The Golden Voyage of Sinbad follows the adventures of the renowned sailor from Basrah, Sinbad, after he comes across a golden tablet dropped onto the deck of his ship by a small, winged creature that is flying overhead.
Though he has no idea what the tablet is or why the creature was carrying it, Sinbad nevertheless takes it up and wears it as an amulet, an act that leads to his having portentous dreams of a man dressed in black and a beautiful girl. While he dreams, an unnatural storm throws Sinbad's ship off course and he awakens to find that he and his men are off the coast of a country called Marabia. Going ashore, he is accosted by the very man in black he saw in his dream, who orders Sinbad to turn over the tablet to him. Naturally suspecting danger, the sailor flees from the man in black and makes his way to a nearby city, where he meets its ruling Vizier, who has been expecting his arrival. The Vizier wears a golden mask in order to hide his disfigured face from onlookers.
The Vizier explains that the tablet is but one part of a three-part map that leads to the fabled "Fountain of Destiny" found in the lost continent of Lemuria. Anyone who finds the Fountain will be gifted with eternal youth, a shield of invisibility, and a crown of great wealth. The Vizier possesses one piece himself, as does Sinbad. The third is hidden away and, along with the two pieces already abroad, is the goal of the man in black, the evil sorcerer Koura, who is responsible for the Vizier's disfigurement (and whose flying homunculus dropped the first tablet accidentally while traveling to deliver it to him).
To prevent Koura's quest, Sinbad, along with his men, the Vizier, and several others, including the freed slave girl Margiana (played memorably by model-turned-actress Caroline Munro), undertakes a mission to find the last piece of the map, pursued by Koura and his minions. Along the way, Sinbad must contend with a wooden masthead brought to life by Koura's magic, an animated six-armed statue of Kali -- likely the inspiration for the Type V demon of Eldritch Wizardry, if there ever was one -- a cyclopean centaur, and a griffin, as well as Koura himself (played with great zest by a scenery-chewing Tom Baker). The result is a terrifically fun film that's one of Ray Harryhausen's best efforts.
Like all films of the genre, The Golden Voyage of Sinbad probably doesn't stand up to intense dramatic scrutiny. The characters are more archetypes than fully fleshed out human beings and their motivations are similarly constrained, but I don't think that hurts the movie at all. Indeed, I think that, because it's clear that what we're getting is a kind of "storybook fantasy" filled with valiant heroes, treacherous villains, exotic vistas, and dangerous beasts, it's easier to let go and just enjoy it for its own sake. That's not to say there aren't moments of solid acting -- besides the aforementioned Tom Baker, Douglas Wilmer is quite affecting as the scarred but noble Vizier -- but this isn't a film about character development or depth of plot. First and foremost, it's a Dynarama spectacle and, on that score, it's one of the great fantasy films of of all time. It's definitely worth a couple hours of your time if you've never seen it or haven't seen it in some time. I think it's a valuable window on the kind of fantasy that inspired the creation of Dungeons & Dragons.