Led Zeppelin....greatest cover band ever..........flame proof suit on.....
You can call all Blues based bands cover bands if you like. As a matter of fact, every musician starts as a cover musician. Lennon/McCartney were no different than Beethoven in that respect.
Clapton covered the Blues, as did The Stones, Hendrix, Allman Brothers, The Who. Aerosmith etc. Next generation of rock covered them. Where do you want to go with this?