I agree with others on here about The Beatles' sheer productivity and remarkable progression during their time together. Listening to Abbey Road, it's almost hard to believe that the same band wrote songs like "Love Me Do"; that's not to criticise the earlier stuff (although I would also prefer the later material), but by the time they split up, they really had created an entirely different sound.
"The chances of each of us coming into existence are infinitesimally small, and even though we shall all die some day, we should count ourselves fantastically lucky to get our decades in the sun." - Richard Dawkins