I think the ship has sailed on a properly done Elvis biopic.
There are actually several actors that i think could have done a good job portraying Elvis had the script been good.
Kurt Russell late 70s thru the early 80s.
Daniel Day Lewis late 80s thru the 1990s
Michael st. Gerard 1990s (Actually played Elvis several times late 80s-early 90s.)
Johnny Depp in the 80s or 90s
Joaquin Phoenix in the 2000s.
Aside from getting a good actor two things could have been done differently to make the biopic better.
1. Portray Elvis as likable instead of depressed, moody or a jerk. (The Kurt Russell and Don Johnson movies did this and then they stopped and went more negative).
2. Portray more things that actually happened in Elvis' career/life.
I was thinking about this a while back that despite so many television movies very little of Elvis' life have been depicted in any of them.
Elvis recording at Sun ( depicted once)
Elvis the 1968 television special (depicted only once in a very bad way)
Aloha (never depicted!!!)