Girl With One Eye said:
Metal Gear Solid, good luck cramming in the whole plot into one movie. Even if they split it into parts, it would most likely have most of it cut out and unexplained.
Holy crap, you picked the one series that would make a *good* movie. I'm surprised there is so much agreement on this point. Have you all never seen Philanthropy? It was a good fan movie, and a real sanctioned movie would actually be awesome.
Basically, any game series that requires significant player input, would probably not make a good movie unless you departed from its canon really, really hard. If a game has choice, you're going to have to lock the main character into one path, and that sort of defeats the purpose. This is why Mass Effect fails the test. But 90% of genres would simply suck: RTS, WRPG, most third-person-adventure like Fallout 3, sandbox games...so on.
The easiest games to turn into movies are going to be the games that are *already* movies. Xenosaga, for one. Metal Gear Solid, for two. Sure, you'd have to turn Metal Gear into a good 4-5 movies just to show the entire plot, but each game could absolutely be a movie, with an optional extra Big Boss prequel covering Portable Ops and Peace Walker. Now, the obvious mistake would be trying to make 1, 2, and maybe 4 fit in the same movie, but that's just stupid. Movie 1 is all about Snake going to Shadow Moses and discovering Liquid Snake's whole shindig. You would have to include a little more about what Ocelot had to do with any of this. Movie 2 is about Snake showing up at Big Shell, more again about Ocelot's plot put in, as well as maybe a bit of what the point of Dead Cell was. Movie 3 is a prequel about Big Boss and might actually come either after 4 or before 2, and also includes some of the backstory you only find through CODEC, like how Ocelot is the Boss and Sorrow's son and all that, and where the Cobra Unit came from. Movie 4 wraps everything up, and everyone dies, just like in the games, except Snake and Otacon and the handful of characters still alive at the end. Hell, you could actually leave out MGS2 and still have something reasonable, so long as you played up the "Snake is an aging clone" thing a bit early, maybe at the end of MGS1.
Basically, Metal Gear suffers from Lord of the Rings problems, in that it has a lot of important details in footnotes/optional CODEC conversations, but if you glean the important bits from those and fit it into the main plot, you could almost make a movie just out of the cutscenes.
JRPGs would also make decent movies, for the same reason. There's already a Persona 4 anime that is pretty much "every major scene in the game, except nicely wrapped into a movie package."