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.
Because video games are a medium that aren't supposed to translate to movies. You can do book to movie to video game, but trying to compress the themes of a many hour interactive experience into a two hour video doesn't work, and video games are too dorky and underdeveloped plot-wise to use as material for movies.