Rolling Stone's listings of whos who are based on reader polls. Many people that may not have a musical bone in their body let alone know the difference between players, players with better talent and viruosos. RS also caters to all forms of music. So when they run a readers poll on whos the "greatest" the poll only reflects who listerners not the musically educated consider to be their favorites. Therefore it is a favorite listing not a talent based listing.
That said many of the greatest virousos over the years have not been responsible for some of the greatest music or involved in highly successful bands. While on the other hand many people that are just players with less than stunning abilities have come up with some truely great songs. Many of my favorite musicians are not at the top of their field but yet are great for the music they were involved with.