I don't actually see you making an argument. From what I can tell, you seem to be complaining that Wii owners are purchasing a game that is currently ranked second highest of all time.
You also point out that Super Mario Sunshine sold roughly the same with a close userbase, but I don't understand what that is meant to prove.
Maybe people buy Nintendo consoles expecting a level of quality in their games, a level of quality that Nintendo tends to fill with its Super Mario series.
They're both great games, and they both should be purchased.
My Games of 2011:
The Legend of Zelda: Skyward Sword
Elder Scrolls V: Skyrim
Super Mario 3D Land
Uncharted 3: Drake's Deception