And almost more importantly, why would your pick make sense to Sony / Microsoft and the game's publisher? Here are a few of my own choices:
Mortal Kombat 2011 - It's a great fighting game, and it could encourage the sale of DLC and / or Injustice.
Mass Effect 3 - Why 3? Online Multiplayer. It's addictive, and the F2P type setup could bring in a nice chunk of change for EA, making it worth their while.
SSX - It didn't sell all that well, but it wasn't a complete bomb either, and it could be pretty fun at times. It's also a great leaderboards game, it might encourage DLC sales, and it could raise interest for a sequel (without death pits, please).
Burnout Paradise - It's an old game, but it still looks good, and who wouldn't want to be able to play a free copy of Burnout with everyone on your friends list?
So, what would you suggest?