At what point did our culture decide that the Beatles were the best band ever?
This isn't meant as snark — for what it's worth, I'm inclined to agree that the Beatles were the best band ever. And I realize that Music Isn't A Competition™, and there really isn't a way to be "best."
The point remains, though, that the Beatles have had more superlatives applied to them than any other band in (at least) the English-speaking world. More than that, these superlatives are applied across a range of cultures (young, old, high-brow, low-brow, a little bit country, a little bit rock and roll) that, if you take a step back, is frankly amazing. The Beatles are musical hegemons, and that's that.
So please take my question at face value: when did people start saying that the Beatles were the best band ever? When did this become an accepted tenet of Western culture? They were obviously a hugely popular band during their existence; did the idea that they were the best flow naturally from that while they were still together? Did, say, Sgt. Pepper immediately seal their legacy? Did it take some years after 1970 for the idea to really coalesce? Was it a product of the red and blue retrospectives, or music criticism's embrace of "top hundred" lists?