Not a fan of either, so most of my info is second-hand. Codblops2 did seem to have a much more ridiculous/fantastic campaign like shooting down waves of helicopters while riding across an open area on a horseback or swinging around in a lush mountain area with I-can-climb-on-anything-nanogloves and Fuck-the-gloves-I'll-use-these swingy ropes.
That seems like much more "pure fun" and seeming to offer more varied/colorful backgrounds than the more linear and gritty Doorfighter. Blops2 even dabbled in moral choices a teeny tiny bit.
Can't say all that makes such a huge difference for me, but I think I can see the general angle where people are coming from.