I think one aspect of Elvis that you've got to remember is that he was a SUPERB showman and a STUNNING live performer. He had an aura, a charisma that all felt - in the fifties. Yes, forget Elvis after his army gig - as John Lennon reminded us often.
But before then: the guy could take a song, shake it, make it his own, and explode it in your face every time.
So in his way, yes, a genius. Don't let the sixties or seventies Elvis fool you, and don't judge Elvis by his declining years. It would be as unfair to judge Beatles material by Paul's 80's output, or Ringo's disco albums, or by the LET IT BE album.