There has been a lot of Mario but each Mario game has been very distinctive. SMG2 will be the first time Nintendo has really repeated a Mario title this year.
However, I'm sick of Mario too. Kirby Golf or Star Fox Basketball would be a nice change and give some of their other licenses some more exposure.
Of course, Wii is a mainstream machine and the mainstream knows Mario, doubt many soccer moms would know Star Fox or Samus or be interested in their games.