Being one of the first to bring up processing power I think I may have to clarify the point ...
I don't actually believe that processing power really matters, in particular when it comes to graphics, but many of the best FPS developers have the complete opposite opinion (they think processing power mattes especially when it comes to graphics). In general, the FPS genre is focused on "Realistic" graphics and in many cases (FEAR) the focus on graphics is so extreme that they give up dynamic environments in favour of better lighting.
The developer I believe are well suited to the Wii's mindset is Free Radical being that their previous generation shooters were more focused on unique style than flashy effects:








