My first CoD game was CoD 2. I've never skipped the campaign in any CoD game. I really do enjoy the multiplayer and zombie portions of CoD but I do like playing the campaigns as well. Also, I am an achievement whore (I'm not bragging, seriously) so I always play the campaigns. I also do play the CoD games on the difficulty the first time through (as I do with all games and again, not bragging) so I like to take some extended breaks from game campaigns to enjoy their multiplayer.
"ZOMG YOUR RADAR IS OUT LOLZ I SWEAR IM NOT 5 FT AWAY" - FFrulz2000 on Scrambler Perk Xbox Live Gamertag: Capatan Azn Man
COD3. But I only rented it for the campaign. Same with COD4. After that, I bought Black Ops after having fun with MP at a friend's house. I never played its campaign, and I didn't play MW3's campaign either. I won't play the BO2 campaign, and I doubt I will ever play another.
COD3. I stopped beating the campaign after MW2, but I got kid close in BO1. I hated MW3, but this game is pretty good for me so far just in MP. I'll be trying the single player out more than likely as the game looks interesting. Plus, y'know, future tech stuff.