1.- Ninja Gaiden (there's alredy an independent movie which is more or less ok, but works more like a musical than like a movie)
2.- Zombies ate my neightbors. (zombies are a hot thing nowadays. zombies + comedy + nerd gamer content = sure win).
3.- Mario Bros (ITS POSSIBLE!!!!)
4.- EARTHBOUND (probably easy cast, enough story but not too long, perfect for a movie from 60 to 90 minutes. if the casting apearance is good and the story congruent with the game it will be great. Also, the comedy has to be there. its relatively hard, but not many special effects would be necessary and the setting its modern america, meaning you can even do some of the footage on your backyard).
5.- Metroid (too hard, but if done right it will rock)
6.- punch out