There may have been better albums, in a musical sense, (but not many!), but for me this album defined the'60s -
1)It introduced the album cover as art
2)It encouraged the publishing of lyrics
3) It was the birth of 'The Concept Album'
4)It announced in a very loud way that The Beatles were no longer a 'Pop Band'
5)It was even an influence on the Prog that was to emerge
I know other bands were involved in the above, but The Beatles put it all together in one spectacular package, and the music was pretty damn good as well!