Few games are currently designed from ground up for touch screen. Almost all are adaptation from console or desktop PC where action are controlled via joystick or keyboard, not very touch screen friendly. But interesting touchscreen games start to emerge. Popular are finger action puzzle, such as Angry Bird/Bejeweled, and the other are tower defense and point defense RTS. Simple RTS is worth checking. From games point of view, they aren’t as deep as desktop games yet, but soundtracks are great. Much more enjoyable than desktop or console because tablet has much better sound system and closer to ear.
Few noteable are: Osmos HD, Eufloria HD, Petri (more here)