My vote goes to either Vagrant Story or Parasite Eve, both by SquareSoft. Both games are pretty short and I could see their stories being adapted into a 2 hour film without having to change all that much. Yeah I know Parasite Eve was originally a book and that book had a movie adaption, but I'm talking about the game's story here.
And the result is usually (1) unsatisfying to fans of the game because it departs too much from the original but (2) too video-gamey for mainstream audiences because of game-specific winks thrown in.
We're also seeing problems from parsing down a several-hour campaign (and possibly a multi-game franchise) into a two-hour coherent movie. The miniseries/serialized TV approach is probably a better medium -- see The Witcher.