I'm not a huge Beatles fan, but what they did do was to continually evolve. Over a short period of time. To have gone from a "yeah yeah yeah" band to some pretty groundbreaking stuff in less than a decade. By groundbreaking I'm not saying good, because a lot of it was junk...the White Album is just bad. But as a band they took a lot of chances and remained commercially viable. Throw into it that they basically stopped touring in what, 65 or 66, but still sold a shitton of records. They obviously had something going on, even if it was just the "it" factor.