I thought the acting question might come up and I couldn't think of the right way to phrase it.
With many of these icons, especially Bogart and Wayne, they played a particular type of character over and over again.
What I think is brilliant about those stars is that within that persona they would surprise us, not with 180 degree departures, but by revealing tough/tender layers. You think you know Bogart and then you get Lonely Are The Brave or the extreme nuttiness of Sierra Madre.
And John Wayne was very reliable as The Duke, but work like The Searchers, True Grit and The Shootist gave these characters new wrinkles and deeper layers.
You don't have to change your looks, walk and talk to prove you're a better actor. Cary Grant made mostly comedies, but adding to that his performances in Charade, North by Northwest and Suspicion and he gets my vote. In all of these films he was undeniably Cary Grant, but he came at the persona from new angles and found new ways to entertain us.