Why this is one of the only CoD games that truly deserve your time and money: For the first time in the Call of Duty series, the infamous veteran mode is actually a fair challenge. Enemy placement is rational, said enemies are no longer just aimbots with brain damage, and they no longer endlessly respawn. The visuals (at least for the time) are impressive. Especially the character models.
There are some great over the top moments to experience during the campaign. You'll fly over a mountain on a snow mobile, chase the enemy down the rapids in a speedboat, and of course; listen to Prisoner 627's suicide run speech towards the end of the game. An awesome bit of sillyness.
Whilst not dragging the game down too
much, the multi-player side is, unfortunately, a different story. Unlike CoD4, there are no dedicated servers, so matches suffer from bad lag spikes, and good luck finding anyone playing outside of team deathmatch and free for all. Spec Ops is the better option. This mode allows you to play an alternative version of select single player missions from both Modern Warfare, and Modern Warfare 2. Either solo or with a friend. My personal favourite is Hidden. A co-op version of the Chernobyl mission from CoD4.
This is the last Call of Duty title (with the exception of maybe Black Ops 2) that actually tried to evolve the franchise above the level of an interactive movie. Definitely gets my recommendation.