Too much hype, too much sparkle
The multiplayer isn't quite what CoD4 achieved, and I'd go as far as to say that its in many ways much worse than CoD: WaW.
I'll start with the Pros:
New perks, redesigned well. Its nice to see some things like martyrdom go away, and the folding of two perks into one, like ninja. It also makes it less mandatory to taking stopping power/deep impact, which is arguably the only combination you could take for rifles in the previous.
New weapons. They're new. Shiney, and fun to shoot.
New maps are well paced.
Basically, the new additions are for the most part nice.
Cons. Get ready for some long reading, I'll start minor and work my way up to the biggest.
New maps lack any definitive best. What I mean is that none of the maps have the iconic arena style of any of the previous. They're simply ho hum. The pacing is fine, the spawns are fine, but its just "acceptable".
The new guns are nice, but after a while you realize they're reskins of the previous. Which is fine, but its nothing to warrant a new game.
The reclassification of launchers/shotguns dramatically change the gameplay.
The kill streak perks are overpowered. They make certain that someone that gets a lead keeps a lead, and more than that, it screws up the flow of a map whenever anyone gets in an AC130. It bogs down gameplay as you can no longer do your own thing, and everyone has to basically hide for the duration, and not actively hunt other players during it.
The worst aspect of the killstreaks are the drop boxes, which, when coupled with the perk that reduces kill streak requirements, allows someone to go two kills in, pull out a missile, and just start the train ride of owning a match.
The point is that the fundamental flow of gameplay is more multiplayer UT/Quake style arena and less tactical. The nature of the new perks are that a person in the lead very often will stay in the lead. Its very difficult to come back from an AC130 if at all, despite being able to shoot it down.
The gameplay is geared more towards unrealistic fast-paced shooting.
Ironsight aiming is no longer a must.
Basically, Call of Duty Modern Warfare 2 is Airstrikes of Duty, Modern Airstrikes 2
Its not bad, its just not better than the first, and in no way does it have any of the revolutionary qualities of its predecessor.