9. Xenogears
There's a lot of things that this fondly remembered classic that merges mecha fighting with side scroller fighting and rpg elements would have going against it in as a movie, but the biggest one is it's plot. You know how wikipedia has a great knack for distilling movie and game plots into a paragraph or two? Well in order to describe what's going on in Xenogears they had to do it in four paragraphs. Even if you could get past Hollywood's aversion to challenging and complex stories in their sci-fi movies, the story is just too big to translate to the big screen in the time constraints necessary for a movie. While one might argue that such a project could be split into separate movies, that's only done for properties that have proven to be successful money makers in the box office like Harry Potter or Twilight. For an unknown thing like Xenogears a studio is going to want a self contained one off that sets up a sequel which would not work for this. Then there's the look of the game's world and characters, which even if you got a studio to back a big budget 6 hour movie with two intermissions would be difficult to pull off. The entire visual aesthetic of Xenogears is very much of the "sci-fi anime space opera" variety which is incredibly tricky to pull off for live action. There's also the factor that a lot of the primary characters have very asian sounding names like Fei Fong Wong or Citan. Asking Hollywood to fund a big budget sci-fi flick with an asian protagonist shouldn't be such a tall order, but it is. The thought of a whitewashed cast of blandly Americanesque protagonists makes this a movie that would inspire many a wished for crotch kicking.