Call of Duty: Black Ops was a lag fest initially but now it has been fixed by Treyarch as was pointed out at BashandSlash, it was due to faulty server configurations. The suggested fix below has been pushed live by Treyarch, and now you will experience less lag, but can’t say no lag.
sv_maxrate “25000” initially set to 5000.
Initially during the game in some rare moments, game would just behave like a slide show, while may behave just fine in hectic stages full of explosions. This issue had been reported both in Singleplayer and Multiplayer, while the patch is in Works, the multiplayer side will probably face lesser issues now with this tweak is live.
If you own a Call of Duty: Black Ops Dedicated Server, restart it and it will now run fine. For any other issue you face, refer to our Call of Duty Black Ops Troubleshooting Guide.