I never quite "got" Elvis until I saw his 1968 comeback special. I was in college at the time (I wasn't in college in 1968, I was in college when I saw a rerun of the special on TV).
Just like that, I understood what all the fuss was about.
I stumbled across this clip a few days ago. "That's Alright Mama" was the first song he ever recorded. He kills it.