Modern Warfare 2 tweaked the bobbing, the speed, the damages and the recoils and improved the graphics. If you play CoD4 and MW2 you'll notice the difference with your eyes closed.
Fallout New Vegas? They tweaked VATS, the ranged and melee combat, the damage system, and improved the dialogue and story. If you play New Vegas and Fallout 3 you'll notice the difference with your eyes closed.
It seems to me that you're 100% shooter fan. Why did you pick up an RPG and then immediately, in your mind, compare it to what you believe is the epitome of FPSs?
Modern Warfare 2 felt exactly the same to me as Modern Warfare. I know some can make that argument for New Vegas as well.