A previous Humble Bundle offered the android port of Carmageddon along with some other games. It plays just like the PC version, and it is enjoyable even with touch controls. Also, i'm having lots of fun with the PC version of Atlantic Fleet; you may want to check out the android version of it, if you're interested in naval warfare etc.

For a quality roguelike rpging, Wayward Souls. My only smart phone game I've got. It was fun, and designed well.
Not for every rpg fan probably, since it has perma-death, but there are a couple of different character to choose from in the beginning, which make the gameplay more varied.