My opinion (after reading several very comprehensive Beatles books)... in the beginning Brian Epstein was simply looking for another act that would be able to crank out "hits." Nothing wrong with that–it's a perfectly reasonable business model. And Brian was first and foremost a businessman, not a music guy. But the Beatles were just way too talented to be limited to being just a "hits" band. As cruel as this may sound, Brian Epstein's suicide may well have been the best thing to ever happen to the Beatles, because once they were out from under his control, they were free to do what they wanted to do, not what Brian wanted them to do. And George Martin was a big part of their post-Brian creativity... he really was the "fifth Beatle" in the recording studio.
My opinion... the Beatles were freakin' musical geniuses. Ok, maybe not Ringo... . No offense to Ringo, but he was obviously not on the same level as John, Paul, and George. A perfectly competent and serviceable drummer and a genuine nice guy, for sure... but nowhere near the level of talent and creativity that the other three were. Compared to the "manufactured" pop stars with questionable talent (if any at all) that rule the charts these days, what the Beatles created is amazing. Like their music or not, but there's no denying they are head and shoulders above the typical rock and roll band.
How many other bands could have created a song like "Blackbird" and one like "Helter Skelter?"