@ Werekitten, silentmac & PearlJam,
I think you're getting into a very grey area in the discussion of control and game design. PearlJam, you've talked about the many actions involved in games like Halo and Gears of War, besides aiming. Werekitten, you've talked about the lack of buttons on the Wii remote, and the interference in aiming arising from gesture control.
To me, each of these things highlights the importance of good game design in overcoming controller limitations. I'm not much of a FPS player, so forgive me if what I'm saying is wrong, but I was under the impression that Halo was such a huge success because it overcame many of the limitations of dual analogue control through intelligent game design choices: subtle auto-aim, gameplay focussed more on movement than aiming, automatic health recovery, etc. The button layout and analogue movement capacity of a traditional gamepad, was used compensate for the lack of precision in aiming. The game design choices highlighted the positives of dual analogue, especially where it was better than mouse and keyboard (i.e. button placement), and compensated for the negatives (e.g. auto-aim and, in many games, a 'quick 180' button).
In the same way, I think that a truly great Wii FPS would circumvent all the shortcomings you've talked about, and focus heavily on precision shooting and simplified control (i.e. the things the Wiimote does better than dual analogues ever can). The lack of buttons on the Wiimote only matters if you make design choices that require buttons. The four buttons (c,Z,A,B) should be enough to design a good, complex game, provided developers think hard enough about how to design gameplay around the controller, rather than start with a fixed idea of what the game should be, and shoehorn it onto the Wii.