I think a lot of games could be the basis for excellent movies. That doesn't mean it will happen. Most movie scripts don't become
good movies. So, for the purpose of this thread, here are some games I think would be interesting to see on the big screen. These are mostly for sentimental reasons and they would have to be directed by me to be perfect, of course.
1. Return to Castle Wolfenstein - this needs to be slightly modified to tone down the outlandish silliness of the robots and demons of the game. That's toned down, not removed. It wouldn't be RtCW then.
2. Metal Gear Solid/Splinter Cell - Pardon to the fans of one of the two for grouping them together. The idea behind these two are rather similar and I think they could make for a very good movie. Someone mentioned MGS as a "futuristic James Bond" and I can agree with that.
3. Broken Sword Series - This series of adventure games could be a lot of fun. Unfortunately The Da Vinci Code will do away with much of the originality these potential movies could have offered.
4. Gabriel Knight Series- This could be an excellent basis for any number of games. Secret tombs, voodoo, werewolves. Oh my!! Not having capitalized on the Gabriel Knight name immediately, during the popularity of the adventure games, just goes to show that there is no coordination or justice in the World. Gabriel Knight could have been a household name like Indiana Jones and James Bond. Those days are over, I think, but I would still like to watch such a movie.
5. Warhammer 40K - This is still mainly a non-computer RPG, but computer games are coming along and who wouldn't want to watch the Space Marines tear up a few planets for the Emperor? This could also give StarCraft fans a fix as they are somewhat similar. If Dungeons & Dragons can make a horrible movie, this should make an excellent one. Aliens multiplied by ten thousand (give or take a few million).
6. Max Payne - Could make for an interesting physchological thriller and action flick. It would have to be dirty and painful. Something like Sin City.
7. Call of Duty - I think Band of Brothers was (is!) an excellent mini-series. It has much more to offer than Saving Private Ryan and Call of Duty and Band of Brothers have a lot in common. Compressing Band of Brothers (by the name Call of Duty) into a movie could be very interesting. But I am a sucker for WW II movies.
8. Deus Ex - This game, like Max Payne, would have to be on the darker, dirtier side. It would make for a nice cross between Payne and Blade Runner.
Please please please (Uwe Boll, are you listening?) don't make F.E.A.R. into a movie. It is already a bad unoriginal game (graphics are sometimes good). Don't do it!
EDIT: sorry for most (all) of these being PC games.