okr on 24 January 2011
I can't give you any recommendations based on own experience as I never play co-op, but maybe these links are useful:
http://www.co-optimus.com/system/1/xbox-360.html
http://www.co-optimus.com/system/11/xbox-live-arcade.html
As you're looking for an RGP, the diablo-style action RPG Sacred 2 might be something for you:
http://www.co-optimus.com/game/872/xbox-360/sacred-2-fallen-angel.html
Here's the information this site has to offer on Tales of Vesperia's co-op:
http://www.co-optimus.com/game/905/xbox-360/tales-of-vesperia.html#
And I agree with themanwithnoname on Lego&Ladies: My niece completed all Lego games together with her boyfriend and they constantly tell me how much fun these games are in co-op mode.
