Interactivity?
I might be wrong, but I think that maybe the plots of even the best games are not really strong enough to support a non-interactive experience like a movie. In a game they work just fine, even admirably, because you are so much more engaged with the whole thing. But just sitting there watching, and Resident Evil becomes 'Mila Jovavitch kicking things in the head' (which I'll pay for, but should probably be in some sort of speciality section).