Wow. I bet Treyarch set out for a much more mediocre goal with Black Ops. Honestly, shouldn't EVERY developer be looking to make the best game possible?
But more realistically, if they simply bring out the same-old, same-old, then they'll still sell a ton of copies, but if they want something interesting and unique, they need something that's similar to what's familiar, but still different.
Why not multiplayer variations on the tactical combat of MW2 Special Ops? A squad of four, one in an AC130, versus eight randomly respawning enemies that are trying to stop them from reaching their goal. Two stealth soldiers are trying to reach a specific target, but the defenders don't know where that target is, and don't know where the stealth soldiers begin.
Just a little thought could make Call of Duty more than a simple killstreak-fest.