I think it is the second most overrated game of the 21st century. The first shall not be named for reasons that are all too apaprent on these forums.
In short, I think MW2 is pretty much utter trash. It's too arcady (unrealistic), too cinematic to be believable, and it feels like a lot of the weapons were just tossed in because, "They could." Hell, the ACR a.k.a. the Magpul Masada has not even passed all of its trials yet, and the civilian version is still in limited production. It may not have even been released yet! I am also not a fan of the, "Hide behind a rock until the icy hand of death goes away," healing mechanic that has not changed since the first Call of Duty.
On the plus side, the story is entertaining (and interesting) to follow. However, the campaign was just way too short for it to really be engaging.