Fun fact: the first choice for john McClane was frank Sinatra as he played the character in the movie’s “prequel”

He was the first choice only due to contractual obligation. Sinatra was in The Detective and Die Hard is based on a novel that was the sequel to The Detective. At the time he was offered the role in Die Hard, Sinatra was 70 years old, and, as expected by the studio, he declined the role.

Others who were offer the role included:

Sylvester Stallone, Richard Gere, Clint Eastwood, Harrison Ford, Burt Reynolds, Nick Nolte, Mel Gibson, Don Johnson, Richard Dean Anderson, Paul Newman, James Caan, and Al Pacino.

When the role was finally offer to Bruce Willis, he had to decile due to contractual obligations to continue filming Moonlighting. That changed when Cybil Shepard s pregnancy cause Moonlighting to go on an 11 week hiatus. Willis was then able to film Die Hard during that hiatus.