While the story in the first Modern Warfare surprised many with its power and depth – moving deftly from explosive to disturbingly quiet moments – the game’s multiplayer was what made it a blockbuster. Jeff Gerstmann at Giant Bomb says that both aspects are back, even if the single-player parts try a little too hard.
Rather than taking a ton of huge big-budget risks, Modern Warfare 2’s multiplayer carefully builds upon the developer’s previous success in ways that will astound people who have spent the last two years learning every corner of every map in the previous game. Instead, the risky stuff is saved for the single-player campaign, which offers tightly packed thrills and rock-solid gameplay, though the narrative is so wild it can get exhausting. [Giant Bomb, 5 out of 5]

Many reviewers agree that the game’s action and pacing set Modern Warfare 2 apart from most other first-person shooters.
The player is both thrilled and disorientated by the constant pace of the action which comes so thick and fast that the player really does feel that death (or at least game over) could come at any second. It’s in this way that Modern Warfare 2, more than any other shooter in the market, both challenges the player’s reflexes and accuracy while at the same time engaging their primal need for survival. It all adds up to some of the best shooter action money can buy. [The Telegraph, 10 out of 10.]

If you’re not interested in playing this game online, be forewarned: IGN was far more excited about the game’s mulitplayer mode than its five-or-six-hour campaign.
For the strictly single player crowd, however, Modern Warfare 2 is surprisingly short, and doesn’t live up to the standard set by previous Call of Duty games. The campaign can be completed in as little as four and a half hours, and the missions make better scenarios and moment-to-moment adrenaline rushes than they do a cohesive, well-told story. [IGN, 9.5 out of 10]

This is where the game really sparkles, according to most reviewers
Multiplayer is every bit as good as you’d expect. Infinity Ward has refined rather than revolutionised the Call of Duty 4 formula, but the key here is customisation. You can create a personalised profile with your own emblem and call sign, unlock your own killstreaks and even unlock ‘pro’ versions of perks if you want to push your character as far as possible. It’s polished, smooth and leagues ahead of almost every other FPS on Xbox 360. [Offical Xbox Magazine UK, 10 out of 10]