Exciting but short single player campaign and brilliant multiplayer make Modern Warfare the best CoD ever.
The multiplayer in CoD 4 features a level system. You level up by gaining experience which can be achieved by killing opponents, capturing objectives and defusing bombs. There are multiple game modes available from your regular Team Deathmatch, to Headquarters and Sabotage. As you level up by competing in matches you unlock different weapons, attachments and skins for your weapons. This is a nice degree of customization and is one of the reasons the multiplayer is so sucessful. You can also create your own class, selecting a main weapon, perks and a secondary weapon. You can team up with friends and join the fight almost instantly, not having to wait a long time like in games such as Halo 3.
Overall CoD 4 is a brilliant game and one you wouldn't want to miss, definitely worth buying if you have Xbox Live.
Gameplay: 10/10
Graphics: 9/10
Sound: 10/10
Value: 9/10
Tilt: 10/10