I`ve never really gotten into the multiplayer, to be honest - it all feels rather repetitive and samey; yes, it`s fluid, and it can be fun at times, but overall, if I'm looking for multiplayer in an FPS, give me Bad Company 2. Interestingly enough, my favourite part of MW2 was the campaign, which I found wildly entertaining. The Co-Op portion of the game was also well done, and my friend and I had a lot of fun with that.
Black Ops, on the other hand, gets a resounding "meh" from me. The multiplayer is pretty much the same, the zombie portion is quite fun (if a little frustrating at times), and the main storyline is a heaping pile of mediocrity filled with some of the most bland characters I've ever seen in a game. The interrogation sequences are particularly grating - there are other ways to create drama apart from yelling and swearing, Treyarch....
Overall, CoD is fine. It can be fun, and it certainly doesn't deserve all the hate it routinely gets. At the same time, I don't believe it deserves its massive fan base, either, something I consider to be one of the most peculiar phenomenons in gaming. Why the hell is this series so popular? Yeah, it's fun, but so are a lot of games....