Let's do this.

Eric Clapton
Aerosmith
Radiohead
AC/DC
The Eagles
Fleetwood Mac
Eric B. and Rakim
Al Green
Crosby, Stills, & Nash (& Young)
The Clash
Bob Marley & the Wailers
Joni Mitchell
Janet Jackson
The Clovers
Roy Brown

Rank 'em, 1-15. Specifically, pull out the artists which are clearly the "greatest", which are clearly the "least great", and which groups are pretty similar.

I mean, if you can't at least convincingly put those artists in general groups, you can't really come in and give an argument for one specific artist.

Then acclaim:

Ranking at DDD: #15
Ranking at Rolling Stone: #3
Q - 100 greatest songs of all time: #25
VH1 100 greatest rock songs: #10
Acclaimed Music: #30

I really like Zappa but IMO he is not worthy of a top 100. I have him around The White Stripes. In the case of Earth, Wind & Fire they could be around the 90th place, they certainly are greater than Rod Stewart or Janis Joplin. In fact, I think that Earth, Wind & Fire = Chicago.

gminer,

We have to note all the variables when we take Youtube into account, such as the multiple versions of the same song. For example, Lennon's recording of "Imagine" is featured on Youtube more than once.

... that is the same with Layla ... but you will see if multiple versions added together the spread does not change by any significant amount ... I would suggest looking at the most popular version is the one over time most folks gravitate towards .... it would be like looking at Smoke on the Water live has over 22 million views v/s 3 million or so for the studio version ... the numbers simply suggest the more popular version and no doubt a good portion of those who viewed the studio probably gravitated to the live version .... Child in Time by Deep Purple is just the opposite with over 13 million views on the studio version v/s 3 million or so for live ... I would suggest this simply demonstrates an unofficial vote of the best versions by those looking to view a specific song ... Take care

Whether live or not or whatever format, it's still the same song, so we still have to look at the other variables to get a clearer picture.

Sometimes it's impossible to get a clearer picture. The Who song with the most views on Youtube was a 1979 live performance of "Behind Blue Eyes". Who would have guessed that? It has since been deleted, so if someone were to do that sort of research today, they would have no idea. For all we know, there could have been another John Lennon "Imagine" upload with 15 million views that was deleted a year ago.

In most responses to this question Janet Jackson is getting no respect. She's more popular than all of them. She has the fourth most Top Ten hits EVER, behind just Elvis Presley, Madonna and The Beatles. She has ten #1 hits which is more than the other 14 artists listed there combined. Her influence is enormous as she was the one who popularized the new jack swing style, which brought the marriage of hip-hop beats and sung melodies to the mainstream and altered the entire course of not just black rock music, but also many imitative the white styles. She may lag behind the others in musical impact, though her stage show was always very well respected, but it's not enough to put her behind any of them. You can make arguments for The Eagles, Marley and the Clovers maybe, toss in Fleetwood Mac, if you want, but Janet probably beats them all, especially when the Eagles and Fleetwood Mac's best areas are popularity and she's better than they are there.

The other thing is, I don't get how Clapton's even considered remotely high among these 15 names. As a NAME, yeah, but breaking it down almost all of his influence and musical impact comes from his work in the 60's within groups, not as a solo artist. Knock those down to their proper levels and even though he was consistently popular, it's not to the level as many of the others. The ones whose popularity is lower have far more influence and impact (Eric B. & Rakim, Roy Brown, Marley, The Clash). I'd have Clapton as one of the two or three lowest of these artists and don't think he's sniffing the Top 100 as a solo artist.

Bob Marley I agree tops this group.
But I'm curious here... Sampson has Marley 73rd in terms of rock influence; Bruce has him 32nd in all of pop music; the rock list currently has him at 35th. Those don't line up.

Fleetwood and Janet I have high because I think they at least have a little influence outside their popularity

(Clash among all punk artists, Rakim among all MCs)

For Janet I wouldn't consider her #1 hits as strongly due to her era. The album was taking over and album sales have to be looked at primarily at that point; singles were used to manipulate radio and market the album. For example Janet had #1 hits from the same album in three consecutive years, as the single releases were spaced out to promote the album over a long period. And by the end of Janet's peak era, the hot 100 briefly became a total joke when "Iris" and "Don't Speak" and a few others didn't even get token single releases and so were disqualified despite being the obvious #1 songs for long periods. In terms of album sales, however, she stacks up completely against all the other popular giants on the list and the #1 hits still have to be at minimum a tiebreaker, but I wouldn't look at her as dominantly popular over the others there with 9-digit album sales, because of dominance on the singles charts of the 80s/90s.

For Marley, listing him with those other three in terms of popularity is totally inaccurate due to Marley's catalog sales, specifically of Legend. The Legend collection is one of the top catalog sellers of all time, selling 10 million copies in the US since 1991 when they started the soundscan tracking. That puts it above anything by any pre-91 artist except the Beatles "1" collection. Of course that doesn't put him on a level with many of the others I put in that grouping, but it does put him well above the three you named.