To be honest, Halo did rework the traditional FPS. It added objective-based gameplay, a conservative two-gun system (some like it, some don't), the genre's first "superstar," and unique multiplayer options. Before Halo, Goldeneye revolutionized a genre that had, until that point, been defined primarily by Doom.
You can argue Halo's overall merits, but I don't think there's much of a question that it gave the FPS genre a shot in the arm in a lot of ways.
I think the FPS genre is conversative ANYWAY. In my mind, there have only been three or four really groundbreaking FPS games: Wolfenstein 3D, Doom, Goldeneye, and Halo. But that's just me.