Apocalipca
If it's done in a way that isn't a total copy and paste and ruins it, then I suppose it would be good. Or maybe a prequel movie that doesn't suck (cough*Rise of Cobra*cough) and start the series from their, or do something like the Resident Evil films.
Some good Examples are:
Professor Layton and the Eternal Diva
The Mortal Combat Miniseries (online on Youtube)
Sonic the Movie
... that's it, sorry.
Anyway, what I would like to see made into a movie is
Pokemon(an actual movie not just a ripoff from the anime)
Zelda
Blazeblue
Okami
Infinity Blade
Street Fighter (a good one!!!!)
Final Fantasy (better than the one they did before and with the graphics from Advent Children)
Dead Space
No More Heroes(?)
Have you seen the Mari bros movie? good actors, bad plot.
Do you mean live action films? (pokemon) cause thatd be cool, as for video game movies you have two options:
Think of it as a movie and not actually a continuation of a story (canon if you will)
or
Think of it as part of the game, chances are you'll spend half the movie saying "yeah right" or "he doesn't get that item until level 12"
As movies most aren't bad, ever see Prince of Persia its actually a good movie.