MW2.5
By now, the Call of Duty engine and graphics the game is based on is starting to look and feel dated. MW3 doesn't have a graphics update over its predecessors and it looks like a 2007 game in 2011. The good news is the controls and engine don't change, and it's fine because they were superb to begin with.
The campaign is both over the top and uninspired. The plot is essentially a global manhunt for one guy and takes from where MW2 left. This game assumes you played MW2 because there's no longer a "tutorial" mission, for that you'd have to play another game mode. If you played Call of Duty before, there's nothing in the campaign you haven't done before. The slow-mo breaches per example, once an exciting part of the game, are now routine. Fortunately, the campaign is short enough to avoid becoming tedious and repetitive.
Special Ops is where more of the improvements were made. Now you have a very fun survival mode that resembles the popular zombie mode from Call of Duty's "even year" developer Treyarch. Special Ops also has an upgrade system similar to multiplayer. These improvements however took one step back, as the co-op so essential in the first Special Ops mode was toned down.
Campaign and Special Ops are just excuses for the real reason people play this franchise: Online multiplayer. This is where you'll see more complaints coming from. Gone is the balanced gameplay of the former year's Call of Duty entry Black Ops, bringing back some of the infuriating problems of MW2. The maps encourage camping, but not as bad as MW2. Some game perks help camping but with the intention you use them for a sniper class, because camping for a sniper is not only acceptable, it's the way it should be. That makes the game more sniper friendly since you can camp now in a vantage point without expecting a n00b tube to flush you out. The new game mode "Kill Confirmed" manages to both discourage camping (the wrong kind of camping, the one you just lay in a corner waiting for someone to pass by) and encourage cooperation, it's a win-win and the only new addition worth your time. Now, more good news. The n00b tube festivals from MW2? Gone. The damn n00b tube is so nerfed, n00bs are going to need a new weapon. The upgrade system forgets some of the innovative ideas of Black Ops and add a head-scratcher individual weapon upgrade system. MW2 forced you to master some weapon attachments in order to get others, I believe this upgrade system encouraged complete mastering of the weapon. The new upgrade system kills that idea, so you can fully upgrade your weapon without ever having to use a particular attachment or perk. Cheaters will find their One-Man-Army perk missing, and boosters will get their tactical insertion in a rank that makes it almost pointless to boost. Gone are popular weapons like the beloved FAMAS (ironically, this game has maps in France), the AUG H-BAR and the annoying Harrier jet.
So let's recap, MW3 is a good game, but it's not also a Call of Duty sequel worthy of full-price admission. The formula is still good, but it's getting stale. The improvements could've well been an expansion pack of MW2. To ask people to replace a game you invest a lot of time and money every year is an insult to gamers. Greed ultimately doesn't pay, thus, this is the last Call of Duty game I purchase.