I've been listening to a lot of old Sun Records recordings from the 50s lately, including Elvis and various other acts.
Elvis' vocalizations and arrangements are unique and recognizable, but no better or worse than the others for the most part.
Now, who would most of the more affluent, record-buying public back then rather look at, Elvis or most of those other guys?
Answer that question to understand why Elvis was leaps and bounds more successful over the next few years than anyone else and then became a visual icon later as well as a result of his formulaic movies that he himself apparently did not care for much, despite the money they made.
Johnny Cash is the other SUN Records act from that time who remained popular over time. The topical substance behind his music has actually aged well and even made him perhaps more popular than ever late in his career and after his death.
Both were most fond of gospel music actually as I understand it.
My wife is the big Elvis fan. Elvis is OK but I'm more of a Johnny Cash fan I suppose if I had to chose.