Another one of these, eh?
Well, if I had the power of the protagonist, I'd choose Saint's Row 2, hands down. All day, everyday, I could literally do whatever the fuck I wanted to. I would have a small army under my command, and I'd be a rich, immortal one-man army myself.
But if I was just myself living in the game, I'd choose Pokemon. Being a trainer doesn't require anything other than the desire to be a trainer. And there's almost nothing else to do. So I would have a wonderful adventure with my Pokemon companions, not a care in the world.