Whether you prefer Single Player, CO-OP or Multiplayer, this game has all three of them. I have reviewed all three parts of the game if you are considering buying this.
CAMPAIGN REVIEW (Single Player):
The campaign is about 6 hours long roughly. It can be shorter or longer depending on your selected difficulty. The story itself is very good and is set 5 years on from Call of Duty 4: Modern Warfare. It is not a Hollywood Blockbuster but at the same time it is not some random quickly written story that was put together in a few hours. Every mission has different objectives and you can feel the climax building up to the finale of the game. Every level is action filled and there is never a dull moment in the campaign. As you progress you will play in different locations in the world such as: Afghanistan, Brazil, Russia, the Atlantic Ocean and the United States. Even after completing the story there are Intel collectables to find and of course Steam achievements. There are also quite a few Easter Eggs in the campaign levels. The story for this then continues on into Call of Duty: Modern Warfare 3
SPEC OPS REVIEW (Single Player / CO-OP):
The Special Op missions are mostly the campaign levels but switched the other way round and with different objectives in the level. There are a total of 23 spec ops missions in MW2. 21/23 of these can be done on your own or with a friend. There are 2 Spec Ops missions that can only be done with a 2nd player. The missions get harder and harder as they go on. Some of the levels in this have been re-used from COD4. There is no matchmaking for the Spec Ops so the only way to find another player is to invite / join a friend and begin playing. There are also quite a few Steam achivements for this like with the Campaign.
MULTIPLAYER REVIEW (Multiplayer):
The Multiplayer is what is considered the strongest part of Call of Duty: Modern Warfare 2. Unlike COD4 this time the game uses Steam Cloud, so your rank will all be stored online and will sync every time you close MW2. The highest level you can reach is level 70 with the addition of 10 prestige levels. When you reach Rank 4 you will have the ability to create your own classes where you can choose your main weapon, secondary weapon, perks and equipment. You can also stick attachments to pretty much all of your weapons on here. You can also unlock weapon camos for your main firearms, which some look very cool when placed on. You have the ability to join friends in a session and vice versa (provided there is space) and host your own private matches for this.
Conclusion: I highly recommend buying this game if you are reading this out of personal interest or if the game has gone up for sale in the future. I recommend playing the Campaign before going to Multiplayer, but it is of course entirely your decision.
Things to be aware of -
There is no controller support for this game.
If you are considering the DLCs, it should be noted that there are less players that 2009 - 2010, so the only two main playlists are the base game and those who own both of the DLCs. If you only buy 1 DLC, you will find very few (if any) games on there.
MW2 Multiplayer has no dedicated servers. It uses a matchmaking system that will pair you up with other players in the same playlist and game mode as you.
This game uses VAC. So if you are banned for cheating / modding, your ban will be permanent. There is no way to lift a ban. You have been warned.
At the time of posting the Multiplayer peak for this is around 10,000 players which is more than enough to find a game and play. Campaign / Spec Ops population doesn't go above 5,000.
If you have any questions or concerns with the game feel free to leave a comment.
Single Player / Spec Ops Hub - http://steamcommunity.com/app/10180
Multiplayer Hub - http://steamcommunity.com/app/10190
Thank you for reading and enjoy the game if you decide to purchase!