I vote Reach, although it was pretty close. Where Black Ops didn't really evolve CoD along much at all (I wasn't really expecting it to do so), Reach added in Armor Abilities (Worst of all: Armor Lock), both of which are major turn offs for me. Setting those complaints aside, Reach is the title that obviously had a clearer vision of what it wanted to be, and what it actually became. The direction on the game was more precise than that of Black Ops.
Both are fun games, but honestly, I really just want me some Skyrim right about now...