I had an xbox but it got the RROD. Now im a PC gamer
Also as for MW3......meh. BF3 will pwn the shit out of that.
LOOK AT THE GRAPHICS !
Firstly: vehicles.
Secondly: better graphics.
Thirdly: Good storyline. (MW is very predictable.....blah blah super important blah blah nuke etc....)
Fourthly: Fully destrucible environment (not like MW where there are indestructible tree's etc....)
Lastly (and most importantly): EPIC multiplayer (64 player maps with PLANES)
EDIT: i found a video that sums up the MW seies perfectly (except for MW1 which was pretty fun)