I agree with KDR on the change for this game, I think it's a good thing. It can't hurt to change things up for one game, and even if it doesn't fit the "spirit" of the series, it does fit the plot. Why not do something different?
I also agree that the series has been over done this generation. What happened to the Nintendo that said the industry was tired of seeing too many sequels? The promise at the beginning of the Cube's lifespan was that Nintendo would innovate and avoid uninteresting sequels, but I believe it went in the opposite direction.
Of course, a lot of it comes down to taste. Obviously some people do like to have a sequel per year, just see Sony, Capcom, EA, and THQ. It doesn't suit me though.