halo 3. The online multiplayer is probably as close to perfect a console fps could be. Coupled with forge, I happily prefer halo 3 over any other fps to this day as long as I can get some friends to play with me.
Warhawk has a very fun multiplayer and the arial/ground battles are some of the most intense period, but I didn't get into it as much as halo probably due to no forge mode. Still I think its multiplayer is one of the better this gen







