As far as single player goes they are about the same.
However with that said Black Ops absolutely trashes MW2 in MP because its far more balanced like non-stacking killstreaks, no stupid perks that allow infinite claymores or noob-tubes or damage pro which makes the noob-tube unstoppable, no death streak rewards, no retarded 10-15 foot knifing, quick scoping is much harder and shotguns can only be primary weapons.