I loved IW's Call of Duty titles for their cinematic story. The Volga River level in COD1 and the British campaign in COD2 were my favourites. COD4 was, to be honest, my first Call of Duty game. I did play some multiplayer for COD4, but not much. I play more Battlefield BC2 than any other multiplayer title, and yes, I will admit it has flaws like any other game.
The single player campaign is boring and uninspired, with too much wiggle room in the levels which kept me from getting drawn into the story. Also, I didn't like the humour, and the archetypal characters are two dimensional, and some of the story sequences like the airstrike in Zero Dark Thirty which took more than a few (frustrating) goes.
Multiplayer has noob tubers like any other, and campers and the occasional spawn rape. But I expect just like those who play Modern Warfare 2's multiplayer for hours on end, enjoyment of the game outdoes whatever gripes it has.
I am actually looking forward to the BFBC2 expansion and I have preordered the Medal of Honor reboot. I like what Danger Close is doing for the single player campaign, I liked the beta, and I am optimistic.