Campaign mode goes to Black ops
Multiplayer is split.
Black Ops- More balanced, every thing implemented can be cancelled out. For example Ghost counters spy plant. Black bird counters ghost pro. Counter spy plane counters black bird. I love how the chopper gunner looks in the game. They reduced the grenade launchers to make it a balanced game. Thats one thing I really love about Black Ops. Perks are more interesting Example: Hardline Pro, Hacker Pro, adding Flak jacket etc. Redundant Killstreaks Chopper gunner and Gunship, virtually the same type of kill streak except one you pilot. They could have added a better kill streak for an 11 KS.
Modern Warfare 2- maps were more fun to play on, less camping corners, more places to snipe from, and play different strategies. Even the maps I hated on MW2 are better than some maps on Black Ops. I love how Killstreaks stack up though. The kill streaks are more exciting as well. AC 130,EMP, Nuke> Gunship,Dogs, and Chopper gunner. In MW2 if the airspace was full you could still call in a pave low on stand by to access other kill streaks. It sucks in Black ops when I can't call in my chopper because there is a helicopter in the air.
Although its not a big deal but spawn music in black ops sucks, makes me cringe almost every time i hear it xd
With that being said, Black Ops is the better multi player but MW2 was more fun to play on.
I could go on more but Its getting late here I'll post more tomorrow.