It was 50 years ago today....

bdp24, I suggest you listen to Let it Be Naked and see if it doesn't nudge you in the other direction.  I find it to be 180 degrees from the Phil Spector version.
Schubert, what you said about George Martin writing the Beatles' songs is simply not true.  He often made huge contributions to the arranging and production.  He did not write any of the songs.  Not one.
I was eleven years old when the Beatles' music hit America.  I was a high school senior when they broke up.  I don't expect to get the same buzz from it now as I did then, but in the words of Brian Wilson, "I still dig those sounds."  I appreciate better a lot of other music from that time than I did then (such as Dionne Warwick singing Burt Bacharach) but I keep coming back to the Beatles.  The biggest problem is that I have heard the original recordings too many times and so I often opt for alternate versions these days but I expect that for me they will always be the gold standard for the 60's.

bdp24
Of course Paul has recognized God Only Knows as a great song and Brian Wilson as top notch friendly competition. But Brian's favorite album is Rubber Soul. Of course the Beatles loved Elvis, Buddy Holly, the Everly Brothers, Chuck Berry (and Little Richard, Carl Perkins, et al).
But that doesn't change the fact that Beatles songs are much more popular today than any of those artists. I am a fan of all of the above, but I can go for 6 months without listening to one song from the Beatles predecessors. I can't go 1 month without having the urge to hear an entire Beatles album.
 The Beatles were also extremely versatile (ie the wide variety of styles of they have excelled in--even in one album (White) ) in a way which none of the artists before them or after them have ever approached.
I love George Martin but he assisted the Beatles on many songs but he was far from  an arranger in the classic sense. As to musicianship, that was one area where the Beatles always beat the competition---not as the best technical players--but as musicians who had the best musicality. The Everlys are a favorite of mine as well and had great harmonies, but there musicians were not nearly as sophisticated and varied in their approach as the Beatles-- especially considering Paul's inventive and musical bass playing on many, many songs and Ringo's tremendously tasteful drumming. George wasn't half bad either. 
I'll take Lennon/McCartney harmonizing (Please Don't Wear Red Tonight, If I Fell, This Boy and many others) as the equals of the Everly Brothers--but different.
I also think Lennon's Twist and Shout voice and his voice in and around1964/65, is one of the greatest in pop history.
I will agree with you that Elvis, the Beatles and Dylan are clearly the big three.
And Richard Manuel was a great emotionally transporting singer.

When it all boils down, and when they did, no band ever rocked harder, then or since, than the Beatles.

"You’d say, you’re putting me on, but it’s no joke, it’s doing me harm,
You know I can't sleep, I can't stop my brain, you know it's three weeks,
I'm going insane, you know I'd give everything I've got, for a little piece of mind."

As musicians the Beatles were rather rudimentary and unremarkable.

As song writers, the Beatles were perhaps the greatest of all time. So many memorable melodies and great lyrics.

I never choose to listen to the Beatles but I heard them so much growing up that they are like nursery rhymes or church hymns - indeliably imprinted in my mind from childhood.