Jimmy Stewart's and Charleton Heston's were "one offs." Really "Sherlock Holmes" was hardly a household name series, though certainly Iron Man is.
And Yul Brenner's Chris was really ONLY known in the first movie. No one thinks of "Chris" in "Magnificent Seven" as the kind of iconic character as they do Rocky or Indiana Jones.
Stallone has now done this same character over a 40 year span. That's pretty incredible. But with Ford coming back the new "Star Wars" movie, he has too.
How about Arnie?
Well said.