Modern Warfare 2 is a fine game and fully worth playing, but offers no improvements over its brilliant predecessor.
In terms of improvements over CoD4, MW2 does not try to do the impossible by trumping its glorious predecessor. Graphically and sonically the game has not been overhauled, although the excellent character detail and animation helps disguise any stagnation with regards to presentation.
The story, too, is a good deal less coherent than CoD4's, with sudden plot developments often dealt with haphazardly and half-heartedly, as if the writers had no belief that the events portrayed could take place. This is not to say that the story cannot be engaging. Key setpieces -such as a bombed and occupied White House appearing through the dust of the battlefield- are stunning; it is just that they are far less frequent than CoD4's key eye-popping moments.
The story mode is of a similar length to CoD4. The story can be completed in about 6 to 7 hours. It is a shame that developers Infinity Ward have not aimed at lengthening the story mode, a fact not helped by the frequent placement of checkpoint. The game in single-player is just a little too short and easy. Of course, to the throngs of fans wanting to play online, this is not much of an issue. But for £45, I expect a decent challenge in single-player.
While the online component of Modern warfare 2 is excellent, giving experienced and newbie players alike equal opportunity to enjoy the various modes, MW2 marks a rather unwelcome (in my opinion) move towards making high-quality videogames with a heavy emphasis on multiplayer rather than creating a challenging and lengthy single-player mode. MW2 is a tremendously good game: it just isn't a step forward over CoD4, or the brilliant PS3 Killzone 2.