I can explain why I think Elvis embodies rocknroll but so much of it is common sense. Why do you think he doesn't? You have to remember that the legacy of those you mentioned in his place suffered much more with each ensuing decade. Elvis is and has always been a phenomenon or Rock. He reached the most people and thus had the most impact.
Your beef is that he wasn't as 'involved' in his own success as you think he should have been. But what does that have to do with the question? Anyhow, why don't you elaborate a bit about his lack of involvement.
As I recall he was one of the pioneers of the 'extended session', staying in the studio longer than was accustomed at the time. It sure looked like he put out a titanic effort performing onstage for years. As well if you look at how much material he put out, no one else spent the time recording and singing those songs. Then you have the movies, the years in Vegas, etc, etc.
