You know I think the reason why they're the "best", at least in Canada, is simple.
A) They exist in stores that are ACROSS the country. The ATH-M50 are available at like one store, I'd never heard of Ultrasone before reaching into this community, and so on.
B) They actually appear in marketing. We've all seen the Lady Gaga, Eminem, etc etc wearing the Dr. Dre phones, so that opens an awareness to the public. I have NEVER seen advertising for Shure headphones.
C) We've got the notion that more $$ = more product. In many situations that can be wrong, like the expensive clothes that last only 2 washes, or obviously the Dr Dre series.
Plain and simple - this probably won't change for quite some time. People are more exposed to media now, there's more pressure by peers and people seem to consistently believe that their self-image is formed a good part by the materials they own/support (West 49 = 'cool kids', to mention one from my highschool).