Not trying to be controversial, but new is not automatically better. Reinvention can result in good things being replaced by worse things as the developers don't realise what worked first time around and more subtly the balanced inter-relationships of those things in the previous one.
MW2 apparently has poor spawn points and some people dislike the emphasis on kill-streaks. Those pirate-style guns aren't popular either.
The Halo: Reach Beta was a serious disappointment. It was like EA had tried to copy Halo without understanding what made it great. All the weapons were crap, all the maps were dull (except perhaps Overlook, but that suffered from overly restrictive sight-lines), the jet-packs were underpowered, armor-lock could kill your team (it should just affect jet-pack avionics), the controls weren't properly integrated so it didn't feel like Halo, you played a disempowered short-arse... need I go on?
So, I predict that after the initial buzz, MW2 & Black Ops will lose players to the classic COD4 and Halo 3 Mythic Multiplayer will still be more attractive in the long run than Halo: Reach.
Battlefield: Bad Company 2 suffers from having too many of its more interesting weapons locked when you start and a limited bunch of maps. Actually, I played B:BC's multiplayer before the sequel arrived in the post and actually enjoyed it more. The best thing about "2" is the spotting system which makes up for the Xbox LIVE community's immature usage of team-chat.
It is rather optimistic, but one game that may dethrone MW2 & Black Ops that no one seems to have mentioned is Crysis 2:
http://www.joystiq.com/2010/04/10/ex-free-radical-crytek-uk-working-solely-on-crysis-2-multiplay/