Sigh...
The problem with Black Ops lag over COD titles is the same issue a lot of CS players complained about during the 1.3 CAL days. In Counter-Strike, recording a demo during your game would cause minor lag issues (it was eventually patched).
In Black Ops, the problem is multiplied by the number of players in the game. The host players console records the gameplay mechanics for the entire game. This is the only major change that occured between MW2 and Black Ops in terms of the way the game works. It's not a frame rate issue. MW2 didn't have latency issues, aside from your typical "Console multiplayer" lag that occurs on most every game. I highly doubt they went in and changed any net code on the game engine... there was no reason to do so. Either revise the way Theater mode works, give us dedicated servers, or scrap it all together.