Well, when I was still a kid playing my nes I had a vision about a perfect game, where you could do anything... everything. You could travel in the city, drive a car, drive it for hours until you reach foreign land or whatever, or simply drive to airport, take a plane and fly... Or you could go to an army headquarters in the capitol of whatever country you were in and start a war. You would have to succeed in revolution first though... Mind you, every aspect of the game would be like you were playing the best game of that particular genre. Greatest car game, the best flight simulator, tamagotchi and a fishing game all in one...
Right now, the best way to implement this would probably be some sort of extension on the xbox 360 gamer card. Whenever you started your xbox, you would immediately go to this lobby game, where you have your avatar wandering in the world... you go to the ice hall and you can start a game of hockey, or you joined a gang which would start your gta. Your friends would be there too online, chatting would be straightforward. When you invite your friend to a game, you'd just walk with him to the race track!
edit: optimally , you'd have the games installed to your hard drive...