its the Wii audience, its the casual, soft gamer audience that's fickle as hell but sure as shit loves the fuck outta Just Dance. In the film industry they've got something they call "high concept", the Wii audience by and large only makes hits out of high concept games, if you need more than a single short sentence to explain it, its gonna tank.
"Mario does more stuff."
"Its like karaoke, but with dancing."
"Its right there in the title, Carnival Games."
"Pretend to get in shape with a videogame."
Its the people that made huge hits out of those games that would buy a really lazy Mario collection by the thousands and be perfectly happy with it, they don't expect much out of their gaming because they sure as hell don't put much into it. This isn't every Wii owner, but it sure accounts for a lot of them.