Games just don't make for good films. It's one of those facts of life.
Because most games have absolutely zero plot, so they have to contrive one in order to slap the marketing name on it.
"There are no good video game movies" (and vice versa) is a cliche that dates back to the NES days. While they're few and far between, it's not a law of thermodynamics. It's not a reason in and of itself that a movie shouldn't be made.
Games like platformers usually have too little plot to carry a movie, games like RPGs usually have too MUCH plot to deal with. This leads to pragmatic adaption or adaptation decay, mixed with corporate influence, and that often spells disaster for what made the original so good in the first place. See Super Mario Bros: The Movie and Final Fantasy: Spirits Within for an example of each.
They're not AMAZING FILMS or anything, but I'd say the first Mortal Kombat movie, the Silent Hill movie and a couple of the Resident Evil movies are examples of movies that faithfully stuck to their source material while remaining financially viable and semi-watchable.
Depending on how good the Prince of Persia movie is and how well it does, that might be another example.
Space marines, huge battles, mind-blowing special effects, an alien menace.... if Halo the game didn't exist someone else would make this movie because it sounds like a recipe to print money in the right hands. It's not thinking Uwe Boll on a shoestring, but Peter Jackson and $150+ million dollars.
