The best game I have on my xbox! I am level 31 in multiplayer, but I'm working on the campaign. The campaign is especially wonderful and I am not even half-way done. Multiplayer is great as well, I love how you need to work together to win. You can't really use techniques learned in call of duty in this game. You will quickly die. Although some things in multiplayer need some updates. Such as the sawed off (I know, I know), but you don't even have to be aiming at the person to kill them in 1 shot..
I was just playing the Battlefield 3 beta on the xbox, and I did not like it. I know that it's beta, but the beta lasts until a few weeks before the official release (What more can they change?). Currently, I prefer Gears of War 3.