I dont think mw2 was that good tbh, i definetely got bored with it pretty fast on ps3...
Camping with an assault rifle and scavenger is just way to easy, the old maps they introduced like crash were awful. In crash everyone camped with grenade launcher and scavenger in the marines side building. The only really new thing they added to multiplayer was changeable killstreaks, but that only made camping easier and more rewarding. Noone takes uav anymore, you just rush to get a 5 killstreak, use predator -> 7 killstreak, harrier -> 11 killstreak, chopper gunner -> win. Or skip predator and use nuke.
After a while people found out it was better to use a launcher to get the killstreaks down, not sure if that was good or bad. You cant camp anymore to get chopper, but harrier and choppers you arent in are useless now.
I have had games where I threw my nade, scavenger -> new nade, scavenger -> new nade. And that 6 times, they should have kept bandolier, scavenger has alot of bad sides... :(