I don't listen to mainstream radio. I recently attended a concert that had artists that play the new and rare type of music that you won't hear on pop music radio. All of these artists fall under the "Alternative Rock" category.

Beck - from California
Cage the Elephant - from Kentucky
Spoon - underground band from Austin, Texas

All three are really good bands. I'm most familiar with Cage the Elephant because I really like their music. My point is that these artists are mildly successful without selling out to the pop commercial formula.

Most of my favorite music has melody, singing in tune (not necessarily perfect though), and imagination in the lyrics and chords and arrangements. It seems to me that many of my favorite songs have sort of a logical flow or sequence when it comes to melodies and chords.

I, too, prefer the music of the 60's and 70's (and to some extent the 80's) over music from more recent decades.

Personally, I like different. I get bored easily, & don't want to hear the same year in, & year out. My music taste is quite wide, although there are plenty I don't like as well, but I like to be open to hear different.

I like to listen to music by artists I do not know, some are excellent , many good, but there is a lot of dross out there. I am constantly amazed at the number of people who have been told, at some point or other, that they can sing, while they clearly have difficulty hitting a note, holding a tune,or memorising lyrics more complex than a couple of repeated lines.
Success in western countries seems to be ensured by an attractive semi naked body and measured by earned income and profits.

Unfortunately I listen to music in my car so that means I only get to hear what is being "sold" by radio stations. I don't live in an area where we have alternative radio stations. I do have friends though that have a much broader musical knowledge than I do so when I hear what they are playing I usually try to pick up a CD and learn more about the musician. I've been musically broadened in this way, I love to listen to Amalia Rodriguez and Cesaria Evora (need to check my spelling) and many others. I also like to follow local musicians and hear what they are doing, especially if they are writing their own stuff.
As far as Elvis - He was new and different, he was easy to look at, he had a nice voice, for us teenagers he was the sign of rebellion against our parent's stodgy music. In other words a gold mine for his producer and manager, and of course for him.
I certainly do not think that a musician has to be successful in the US or UK to really be a success. But like everything else packaging is shoved down our throats and it is what is made available to the masses.
BTW - give me the names of your music groups here on Agnostic as I'll sign up!

Must be by the number of media playings. If any comparison is to be made it must be something everyone can count ( maybe with the media stations or magazine's help).and therefore check upon.