Why is the list of "all-time great artists" limited by this: "based on all charting titles from August 1958 through July 2008." How is this narrowly-limited time period consistent with "all time"?
Surely there have been great musical artists in the centuries prior to August 1958. Why the snobbery of the limitation to only artists from 1958 onwards?
This is just a guess on my part, as I have not examined the site all that much yet. Perhaps it has to do with the advent of pop-rock (and not necessarily popular) music? I realize the Sun sessions (and what Haley and a few others did) pre-date the beginning of the yearly range that is furnished slightly, but maybe that (and the fact that fifty years is a landmark number?) may have something to do with their criteria. You do raise a good question.
All one has to do is click that link and see that the point of the list is to celebrate the "Billboard Hot 100's" 50th anniversary. The ranking is 50 years old, and the list isn't a critical one, it's based on the factual data of the "Billboard Hot 100," which, ironically (it's actually not ironic at all), only goes back 50 years.
No where do they claim it to be the final word on music or music artists. It's a list of "The all-time top artists of the Billboard Hot 100."
Especially as 'all time' includes, by definition, all future time as well. What does Billboard Magazine know that we don't? Is this connected with the black hole scare? I think we should be told.