The story is a lot simpler than MW2's, with the main objective being killing Vladimir Makarov. There are a couple of plot twists, not as bad as Ghost and Roach being killed by Shepherd in MW2 but ones that fit into the Modern Warfare trilogy's story amazingly well.
The characters are much more developed then those of MW2's and the relationship between Price and Soap is really good (no homo). Makarov is a bastard and you will hate him by the end of the campaign. However I felt that the SAS and Delta Force members were not as developed as Price, Soap and Yuri.
Overall I think this is the best storyline in the entire Call of Duty series, with an amazing sense of bad ass motherfuckery, epic sadness and an amazing sense of destruction and scale seen in the recent Transformers Movies.
The gameplay is basically the same as MW2's (which isn't a bad thing), however sometimes you can feel overwhelmed by the sheer amount of enemies thrown at you. New sections come along to keep it feeling fresh and not just turn it into a Time Crisis style shooting gallery, including dragging your team mate through wounded streets, controlling an AC-130 gunner and an epic car chase through Paris.
Overall the gameplay is great, however some sections start to run stale when you just have to keep killing waves of enemies. However it gets varied by the things I mentioned above.
The Graphics are good and are definitely an improvement on MW2s. The game always runs at 60FPS meaning that the action never lags or slows down. One thing that seemed greatly improved on was the lighting and character models, both looking suitably realistic.
Overall, the graphics are good but I don't think they are up to the standard that 2011 games should be. I think this game should be the last game that uses the old id tech engine and that they should create their own, however I know its not essentially Infinity Ward/Sledgehammer games' fault and more that of Activision and the time constraints that they give the team.
The soundtrack is absolutely amazing, giving a more epic feel then Hans Zimmer's MW2 OST. The music really compliments the campaign and nearly brought me to tears at a certain moment in the game. Absolutely brilliant, one of the best game soundtracks I have ever heard. Well done Brian Tyler... well done indeed. (Below are two examples of the soundtrack)
All together, I think this is the best campaign of the CoD Series and gives an amazing, epic cinematic feel. Even if you don't have online, MW3 is a definite must buy.34.5/40