Besides "new" weapons (which all are based on something old due to the time era), Black Ops brings nothing innovative to the table.
The game modes are still the same. Despite there being a custom game mode, the limitations prevent it from really being anything but Team Deathmatch. There is loads of new non-gameplay additions, but most are end up being vile pictures of dicks and animal orgies. It shows you who plays this game.
If you had no problem with MW2's twitch gameplay and easy kills, then stick with it. Black Ops has zombies in it, so it keeps me coming back to it. I occasionally play MP, but people rarely play HC S&D.
Also the lag has been a huge issue. It causes a bad case of hit detection error. Who ever is Host, gets an unclear advantage.