1st party is definitely Wii. Whether a boon or a bane, there is a reason why Nintendo software sells so well-they really are the best there is at what they do. If they were a third-party, whatever system they developed for would be my pick.
3rd-party Microsoft right now. I just love Gears, Mass Effect, Bioshock, Assassin's Creed, Call of Duty 2 and 4, Condemned, Ninja Gaiden, and others. Though I can see how some people would make a case for Sony, too 







