The Rainmaker
Elvis and Hepburn had far too different accents to play siblings....
Thunder Road
Robert Mitchum, who I think produced this movie, wanted Elvis Presley to play his younger brother. Colonel Parker, again, stopped it because he thought Elvis Presley in a movie about moonshiners would be bad for Elvis' image. Makes you wonder how many times Parker stopped these opportunities out of fear of losing control of his meal ticket instead of what was best for his client as a good manager does. Robert Mitchum ended up using his son, James Mitchum to play his brother.
The Defiant Ones
Elvis Presley was just getting started in the movies and was getting good reviews for what he had done and had begun to take acting lessons. It was his ambition to have success as an actor and his idea of who to model himself after was Marlon Brando. He wanted to be in this with Sammy Davis, Jr. and it would have probably advanced his acting career. However, good old "Colonel" Tom Parker talked him out of this one too. As noted earlier, Parker pretty much screwed up Presley's acting career and this must have weighed heavily on his mind when he began to sink into depression before his untimely death. He trusted Parker too much and paid for it.
West Side Story
The original idea was Elvis and other rock stars playing all the Jets and Sharks...
Bus Stop
Don Murray got the part that Elvis Presley could have had.
True Grit
This was John Wayne's movie but Parker wanted Elvis to have top billing. Glen Campbell got the part that Elvis missed out on.
A Star Is Born
Barbra Streisand personally asked Elvis Presley to be in this movie and Elvis was excited to be in it until Parker blocked it by wanting Elvis to have top billing. Ms. Streisand was producing the movie so that was not going to happen. Kris Kristofferson got the part.
It is too bad the Lady Gaga Bradley Cooper version repeated this, Cooper shoulda impersonated Elvis in the remake
Midnight Cowboy
When Elvis Presley's name was considered, the producers and writers offered to rewrite the movie so it would be suitable for Elvis Presley's fans. Jon Voight got the part.
Missing from the imdb
The Party - Peter Sellers played the lead
The Hank Williams Biopic... Hank's widow did not want Elvis overshadowing and the movie was delayed until 1980
Hank Williams: The Show He Never Gave with Sneezy Waters
1980
Grease
Frankie Avalon played the Teen Idol
The Grease cast learned Elvis died the day the Look at Me Im Sandra Dee Rizzo song with the Elvis Elvis let me be, keep that pelvis far from me line..