Most people grow out the phase where they think it is cool to own the extreme or unknown (whatever the hell the X is supposed to be) Box. Does not surprise be the key demographic for the Xbox is and always has been pubescent boys.
This also clearly explains why the seasonal surge the Xbox gets each year.
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut