Cowboy Bebop has a game in Japan, but an action/adventure game with gunplay could be awesome. Maybe you could get a bonus if you act in time with the jazz music.
UncleUlty said:
Code Geass would make for some bitching Turn based stratgy ala Advanced wars/Fire Emblem.
So very yes. The geass also needs to be a gameplay element. Something like that might already exist, I'm not sure.
Gurren Lagann without question needs a game. It's a show about ridiculous giant robots doing ridiculous things with a ridiculous power source. And it has drills. Of course it would kick ass.
It has several games to begin with and doesn't seem like it would lend itself to a good game, but if you use the whole girl-who-subconsciously-bends-reality thing well and have some good action and adventure elements, there could be a good game if you focus on Itsuki and Nagato along with Kyon. I for one would like to play the fight between Asakura and Nagato. It would be hard with a non-actiony anime, however.
A lot of these anime have games, but they are cheap cash-ins. Someone has to make good games out of them.
And someone needs to make Yu-Gi-Oh The Abridged Series: The Game.