Campaign: black ops 2 was one hart braking game with Hart stopping moment's. The campaign is great and if you want to know more about the campaign like get a taste of it you can here: http://www.ign.com/wikis/call-of-duty-black-ops-2/Multiplayer
Battlefield 3 had more war moment's, so if you like a game with no-stop action, Battlefield is for you.
Multiplayer: Black ops 2 was more funner with all the game mode's and thing;s like that. But if you hate
people who trash talk, DO NOT GO ONLINE. This game has people trash talk all day every day, In witch i understand getting killed. but this game had a fun over all if you are looking to play with friend's.
Battlefield 3 has a more army type of way. In multipayer you can drive jeep's ride tank's, fly helicopters and also fly jets and much much more. This game is a realistic game. if you get shot your done. you will not be able to escape a shoot out 50% of the time.
CO-OP: battlefield 3 has a co-op system where you fight a-i kinda like campaign but a tad bit harder.
Black ops 2 has ZOMBIE"S. this is a must have in the call of duty serise or so i think. zombie's is a blast with a lot of gun's ammo and zombie's with up to 8 player and 4 player co-op. black ops 2 will win the fun in co-op but is battlefield ore realistic? Yes but black ops 2 won co-op