Let's talk MP.
First off anyone that compares COD to BF is loving handicapped the games aren't even alike unless you are talking about the single player (We are not talking about Single player but BF3 vs. MW3 BF3 turns out to be the lesser of the two evils when it comes to that.)
Now we're talking about new COD not old COD (Old COD being everything before MW)
COD MP is pretty much a loving poking fight and whoever sees the other person first/gets lucky wins, the MP is fun stuff if you are looking for a non competitive game where you really don't care if you win or not. Killstreaks keep the game mildly interesting but they are all about luck to get them. (Unless you are extensively planning on how you are running around the map.)
The only really bad thing about it is the fact of how loving generic it is, almost all the rounds are the same and you ether really loose or really win.
All the new games are the same game with a different name smeared over it and some different maps but besides that they are the same.
All in all COD is not a bad game (MP) and anyone who says it is doesn't understand jack stuff about what makes a good game.
Also SP sucks massive donkey rooster.
Also to clear up how BF3 is nothing like COD: There are a few things similar:
1. They are both war games
2. They both have guns
3. They both have...People
What makes them diffrent:
BF3 has huge ass maps where COD is all about an arena deathmatchy style.
How you should play the game is completely different where COD you can run out take bullets and gun people down BF makes you take cover and stick with your medics
There is other stuff but all in all they are completely different games.