Black Ops was pretty fun. The Single player was worthy of mention, but... sorry, I'm a zombie whore. I loved Zombies. I loved spending hours playing for the Easter Eggs, and it could get really really tense.
If you've played World at War, you've played the series. MW2 and MW3 were uninspired, and didn't really offer much new to the series. The support wasn't really there for multiplayer, and they're essentially clones. The worst part is, everyone knows it and still buys them. The up side of them is that, because of this, they're reliable. You know what you're going to get in advance, and you can rely on the developers to maintain a consistant level of quality, even if not a consistant level of innovation.