i really don't get why people complain about the over usage of mario as a brand. mario platformers are totally different from mario kart which is totally different from mario party which are all different from mario and luigi. i would even argue that the 2D and 3D outings are very different from one another. all those games are in different genres, the only thing they share is the characters. and that doesn't matter for the gameplay. i'd never pass on the new mario kart because i just played mario vs. donkey kong before...
in addition, i view DK, mario, wario and even yoshi as independent franchises. yes, they all appeared in games starring the others but over time they pretty much evolved into their own thing.
using the established characters in new titles is not a bad move by nintendo. familiar faces lead to more sales so nintendo can experiment with new kind of gameplay experiences without having to fear low sales due to the introduction of a new ip.
however, i'd like to see a new ip nonetheless
p.s. i hope this post somehow gets my points across... it's pretty late here