There are two XBLA games in the "Big button enabled" games category called Tower Bloxx Deluxe and Are You Smarter than a 5th Grader? Check it out:

http://www.xbox.com/en-US/games/catalog.aspx?sd=0&r=0&g=116170000&c=10&xlm=0&h=0&p=1

I have Tower Bloxx myself and love using the big buttons to play because it's a simple (yet addictive) one button game play - simply drop bloxx! The controllers come especially in handy during multiplayer games with the family or when you have party because each tower is assigned to the big button of the matching color. No trying to figure out whose controller is controlling which element of the game. I love it!