Funny thing about Indiana Jones is the studio wanted Tom Selleck but he was too busy with Magnum PI. Here's a deepfake someone made to give us an idea, although who knows exactly how he would have approached the role and no matter the technology, those are still Harrison Ford's expressions and mannerisms.Harrison Ford -- Indiana Jones
My list would include:
James Earl Jones as the voice of Darth Vader. The original actor had a formal British accent that just wasn't as menacing.
The original Ghostbusters cast. Bill Murray was a replacement for John Belushi who died before filming, but I don't think the movie would have been as much of a classic with John. He was great in Blues Brothers and Animal House, but Ghostbusters had a different kind of humor that Bill is/was great at. And of course, Harold Ramis and Dan Aykroyd were amazing as well.
Someone mentioned Mel Brooks, so I thought of Gene Wilder and Cleavon Little in Blazing Saddles.
Matthew Broderick in Ferris Bueller's Day Off
Peter Sellers in just about anything he did
Jack Nicholson in The Shining, One Flew Over the Cuckoo's Nest, among others