Did a Google search for actors who played Marines, and found the below site. But I'm puzzled by it. Maybe I'm wrong, but Charlie Sheen was in the Army in "Platoon". And John Wayne wasn't a Marine in real life. Just a couple of blaringly wrong "facts" I found on this site, and a prime example of how you have to take facts researched on the internet with a grain of salt.
http://neohumanism.org/l/li/list_of_...in_movies.html