Definition of best is what makes this hard for me:
While I prefer MW2 to Black Ops (multiplayer wise), MW2 is outside the window and Black Ops DOES have a ton of content as someone else says. Multiplayer is also fun as well, so I might say it was the best.
The single player campaign was sub-standard IMO though, so for Single Player I'd have to say Reach, the pacing and story were great, the lead up to the finale was fantastic and the actual ending was EPIC. So I might say that Reach was the best.
ON the other hand, no shooter took a fresher approach to the whole genre then Bulletstorm - a game which rewarded you for NOT repeating the way you took out enemies...in that regard I would say Bulletstorm.
Sadly I have not yet had the opportunity to play KZ3 or Homefront yet, so can't comment on how they would fit in the spectrum.
That means it's been a good year for shooters!
