You act as if all the 360 fans sprouted from no where... Most people who own a 360 have owned a N64. Most console gamers who are old enough all started off as Nintendo fans.
Ive seen many many 360 fans that were looking foward to it because they "remember from back in the days".
Btw, Nintendo does not own the rights... Not even a fraction. Activision owns the rights, but Activision said that they wanted to keep their relationship with Nintendo solid so they asked permission but Nintendo denied even though Microsoft was willing to compromise.