There have been a few satirical "reviews" of the MW3 plot that have the effect of casting the general plot structure of the Modern Warfare series into relief.
In general, there tends to be some similarities between the overall structure:
- A training sequence where a new soldier or member of a special forces team gets put through their paces (the game's tutorial is usually framed this way)
- One plot thread in which there's a special forces team tracking a bad guy or other criminal mastermind
- Another plot thread in which a group of soldiers is engaged in front-line combat (usually against the Russians)
- A "shock value" scene in which innocents are killed for the sake of upping the dramatic effect of the story (ie, "No Russian" in MW2)
- A major setpiece in which something bad happens to a notable landmark or city (Atomic bomb over Washington, destruction of the Eiffel Tower)
It's really up to you to decide if there's enough overlap to call them derivative, or if you think the changes make it fresh enough to be fun to play through. There's no "right answer" as far as I'm concerned.
Tangential to this is the reuse of gameplay elements. Some of the common gameplay elements generally include:
- A vehicle sequence, usually on rails
- An air support sequence
- A sniper or sniper support sequence
- A 'silenced' or 'sneak' sequence
- Many long hallways and close quarters fights in bombed out locales
- A set of common weapons (M16, AK-47, RPG, etc)
- This building
When it comes to this stuff though, these pretty much characterize any military action game in a modern locale, so I'm not sure how fair it is to say that MW3 is recycling this from MW2; they're all borrowing it from each other.