ideally you would have more games that work well with the touch controls and whatnot rather that relying on traditional controls. It is similar to the Wii problem where they release existing styles of games that control worse to do the gimped control method. plants vs zombies is one I'd imagine controls well with the touch controls. on the ipod touch, that spider game played well and just used swipes to control.
has anyone tried Mirror's Edge on the ipad? videos made it seem like that one flash game but more involved.
I see minigore mentioned above and that game is really fun on the ipod touch. one of the only ipod/pad games I've played that have nice fake analog sticks.