I agree. I really had a lot of fun in Blops2. Between multiplayer and zombies, I never even played another game.
There were some issues with MW2, like the ones you stated and crazy grenade damage (which plays into the OMA).
I use an AK in every CoD for nostalgia reasons, so I obviously enjoyed the AN-94. One of my favorite smg's in CoD history is probably the pdw... that mag size, little recoil, and good iron sights made it so fun to use. AN-94 and pdw were the only guns i used towards the end of Blops2, in multiplayer or in the high rise zombies map.
The lag was definitely an issue, and I had horrible connection at the time, so I stayed frequently frustrated with it. I was doing the same with killstreaks. Once you put some of the high ones up people would leave... but using low/medium ones and getting gun kills would still rack up the numbers.