Music is entertainmentand we usually base ability based on popularity.
Man, if that were true some of these chapman stick playing basement goblins would be playing sellout arenas rather than.. well.. their basements.
I am not a fan of Nickelback by any means at ALL. I can comfortably say i think they suck. But that's my own opinion.
When you start to argue things like "popularity within music" you touch on SO many different things than just musicianship. There's the whole connection side of things, marketing, aesthetic and so forth that contribute equally to a bands total popularity.
I've always just held the possition of stoic indifference. I play music that i like and that i would want to listen to and that's fine for me. Good on Nickleback for doing something that, i would assume, they love as well. Just do whatcha do the best you can and sleep better because of it.
I never said Zappa was not a great musician. And I would consider Zappa rockstar, even though he does not play conventional music. 

