I've fallen into the CoD trap for the past 5 years, I'm not taking the bait this time. The campaign was written by a 14 year old, the co-op gets repetitive and boring and the multiplayer turns me, for a brief period, into a pyschopath willing to kill and wanting to do unspeakable things to other peoples mothers and sisters.
This is pretty much my stance on the series, too. Multiplayer is great when you're winning, but absolutely the most infuriating thing ever when you're losing to all the people using unbalanced weapons or broken loadout combinations. Plus, the games see very few changes from one iteration to the next.
That said, I think Black Ops was much better than MW2 and MW3.
This, to me, helps illustrate a couple of things that make Halo the better series:
1) Large steps, some of which have been highly innovative for console shooters, from game to game keep the series fresh.
2) With Halo, I have fun even when I'm losing.