Sinatra didn't much care for Elvis in the 50's
and I imagine a lot of current day artists are jealous that they aren't as successful as Elvis.
He set the template, not only the most successful singer, but the one who turned that into a successful movie career too.
no matter what else can be said for his films - he was the highest paid actor for many years in Hollywood. Few other people could have been the lead in 28 consecutive money making films.