Ian I would agree with you except, I don't think Nintendo needs to worry about having an exclusive "normal FPS." FPSers have been on every system, and it doesn't matter if they are exclusive or not...just that they are good.
However, original ideas and concepts aren't on every system. Geist was a really great original game. Yet, it needed to be better thought out. It was like the development team had some ideas, but couldn't wrap their brains around how to best execute the ideas into a full fledge game with story and great level design.
I played most of Geist, the final levels were quite difficult, and I could beat them. What I noticed from the game was almost brilliance. What I mean is that the game had some many great ideas that worked but did not shine. I guess I would say the execution of everything was at 70%.
If Nintendo gave the game a second chance, I think it could be really great. Retell the the same story, but add more to it. Get out of the research/base area faster and have more "real world" activity. Have a really fleshed out multi-player game with online play. I loved the idea of setting up traps and using inanimate objects against your enemies...I want more of this in the game.
If you created a new Geist game which reached about 90% execution on all the potential that was in that game, you would have one of the best FPS/A games there is...and you would have a hell of a multiplayer game.
Then we could allow EA, Free Radical, Ubisoft and all the 3rd party developers handle normal FPS for the Wii.