I'm picking Brawl on a whim...it's more likely that GTA will outsell it, but bets aren't fun if you go for the typical winner.
LEFT4DEAD411.COM
Bet with disolitude: Left4Dead will have a higher Metacritic rating than Project Origin, 3 months after the second game's release. (hasn't been 3 months but it looks like I won :-p )