Saints row 2, Magicka, Portal 2, Dead Rising 2.
All co-op mode, all be it Saints Row 2 isn't the best of console ports but probably the most fun out of the lot.
All brilliant if you are looking for fun over super serious games.
Dungeon Siege 3 has quite good support for the game pad, lots of people didn't like it, as a co-op game I enjoyed it.
No idea how any of them play with a pad though, used KB+M for them all.