the notion of sequel isn't inherently evil to me. nor is re-using a title or a character or a franchise (etc). in many cases, its a good thing -- and certainly one we can expect.
what i notice with many nintendo "sequels" is that something big is flipped around. there are typically some big risks taken, even with their major names. sometimes it works out for them, sometimes it doesnt.
nes to snes saw some "simple" presentation upgrades. but from snes to n64, a whole new dimension was added to the games, literally, making them, essentially, entirely new.
many expected the transition from n64 to cube to be the same type of "simple upgrade," but nintendo made efforts to change things up even more hand. the cube zelda had an entirely new style and story. the cube mario was in a whole new world equipped with weapons. metroid evolved to a 3d, first person perspective. donkey kong went from a platformer to a peripheral-based adventure. even mario kart took a new spin, changing the dynamic of the game with a second 'rider.'
granted, some of these efforts to keep things fresh ended up backfiring, as some people rejected the change. but at least it wasn't just "the same ole, same ole"
with nintendo's new systems, wii and ds, everything changes, deliberately. the entire interface with the medium is shook up and altered.
sure, its "just another mario," but its a mario unlike any before in some of the biggest ways possible.