I don't remember where I've said this before, I think
http://www.codenamerevolution.com/, but the Wii is a phenomenon. People go to the store to get one. Not a 360. Not a PS2 which only costs $150 or a $100's Gamecube. The casual gamer doesn't 'see' that the 360 is a more expensive machine and you'd get more value for your money tech-wise. They know you can only get the unique controls on the Wii, so the Wii gives more value for your money fun-wise.
They simply want a Wii.