Wow, I would like to know what answer you got for this!
After scrubbing imdb, I discover that Elvis starred with Howard McNear in three films. However Howard died in 1969, so he can't be the answer you're looking for.
If you're thinking Kurt Russell (and you want people to actually guess), you should be a little clearer about how broadly you're defining "Elvis movies." Only one of the three films (It Happened At The World's Fair) actually starred Elvis. The movie "Elvis" from 1979 is a TV movie, not theatrical, so may not count in many people's books. And of course there's the execrable "3000 Miles to Graceland," which didn't feature Elvis as a character or actor at all.
Still, intriguing question. Certainly Kurt is the most Elvis-like of living actors. Maybe a remake of Viva Las Vegas with him & Reese Witherspoon?