Not questioning the superiority of the Beatles, but after the shennanigans "Sir Paul" pulled at "Live 8" I wouldn't say they knew when to quit. McCartney has been a whacko environmentalist since the 70s, Lennon was more like Lenin through the 70s until he was shot.
Fortunately George and Ringo were my favorite Beatles. They just got rich, polluted their bodies with drugs and alcohol, and shut up about activism.
Paul is definitely an ass. I heard years ago that he and Linda wouldn't employ meat-eaters on their tours. So much for that tolerance and diversity, eh?