[private joker]

Films are collaborative efforts and this question just simplifies the issue too much. However, you failed to include Producer, and he's the guy who gets the Oscar for Best Picture. He generally puts the project together, including hiring the director, overseeing the post-production, and helping develop it in prep.

Artistically, a film is generally considered a director's vision, so he's ultimately responsible for what's on screen. But more often than not a good director can't save a crappy script, while a lame director can still come up with a good film if the script is strong.

There's really no satisfactory answer to this -- I'd say Director/Producer/Writer are all equally important, with Cast/Photographer/Editor coming in very close seconds.

And, of course, it really does depend on the film.