Some are going to kill me but I think Jonathan Rhys-Meyers did a great young Elvis, what was crappy and many bashed about it had to do more with the scrip not his performance, that regardless of his unfortunate comments on Elvis latter on. Yet, I said young Elvis, when he got to play a more mature Elvis on the '68 Comback special he didn't seem to have the dramatic skills to match Elvis intense character of the latter days. The If I Can Dream was most the syntomatic as he is far away from the actual drama of Elvis original performance, and he simply goofed it. Yet, he did great on the easy going 50's Elvis/ early 60's.
I think Johnny Depp would be a fantastic post '67 Elvis, but, its getting late, 5 years from now, and Johnny will be too old to play any Elvis.