Black Ops was way too over-hyped imo, the campaign was terrible. The story was so poorly written and the cut-scenes and cinematics were hugely frustrating, every goddamn 2 minutes you get stuck in another 10 minute cinematic... if treyarch stopped trying to ram the crappy story down your throat and just let you play the game then it might have been more fun...
As for the online... waaaay too gimmicky, I mean, a ballistic knife... really? Explosive crossbow bolts? Oh, and don't even get me started on the bloody RC car...
I will give treyarch credit for not making killstreak kills stack, it balances things out a bit more, but its ruined when they add stupid stuff like RC car, it's just frustrating instead of fun.
I don't like the way they've made everything more cartoony in appearance as well, MW2's look was spot on in comparison.
The best thing about the online for me is the fact they've introduced split screen online multiplayer, it's great if you have friends round and want to play online together without having to take it in turns
The major saving grace though is Zombies, that in itself is worth buying the game for... Especially if you have 3 friends playing with you, it's absolutely brilliant. The whole sense of humour behind it was brilliant as well, I think the campaign took itself way too seriously, if it was more like zombies it would have been much better