Gerard Christopher

He was chosen to play Superman in Lois & Clark: The New Adventures of Superman (1993), until the producer who hired him read his acting resume and discovered that he had previously starred in Superboy (1988). According to Christopher, the producer said, "You've done this already, I want someone who hasn't acted before!" He was then dismissed from the room, and the role was given to Dean Cain.
When he made his debut as the title character in Superboy (1988), he was 30 years old, making him older than Christopher Reeve, Dean Cain, Brandon Routh and Henry Cavill when they made their respective debuts as Superman.