A respected analyst says that it's entirely possible that Call of Duty 4 will outsell Halo 3 as a result of COD4 being available on more platforms. Also, it's a widely-hailed game that has a ton of pre-orders and is already sold out at most retailers. Now, since Halo 3 broke all sales records when it came out, that's a pretty bold prediction.
Still, Call of Duty 4 is one of those games that, it seems, almost everyone can get behind. The advance reviews were excellent, and players seem to really like it. Does that mean that it will be the highest-selling game of all time? We don't know, but it almost certainly means there will be a Call of Duty 5.
The Escapist: Analyst Predicts Call of Duty 4 To Outsell Halo 3