We’re not sure if it came up because of the interest in Peter Jackson’s terrific documentary about the Beatles or maybe it was in it, but Paul McCartney said this about The Rolling Stones:
”I’m not sure I should say it, but they’re a blues cover band, that’s sort of what the Stones are. I think our net was cast a bit wider than theirs.”
Mick Jagger had some mildly snarky comments about concerts but also called McCartney “lovely” and meant it.
McCartney wasn't wrong though. The Stones really admired musicians like Muddy Waters and Willie Dixon and for a long time were basically a cover band.