John Wayne and Clint Eastwood are the two actors whose names always spring to mind when western movies are discussed. They both starred in some epic westerns, and without them the genre would just have not been the same. Movies such as The Searchers, Red Rivers, 3 Godfathers, Unforgiven and a Fistful of Dollars were created with these actors in the lead roles. They transformed how the movies were made and they really managed to put on stellar performances. Olivia de Havilland and James Stewart also had great careers as western actors. They performed so many different kinds of roles and appeared in so many different movies. The bottom line is that they are two great actors who did the western genre a great service. Havilland appeared in Dodge City and Stewart starred in The Shootist and both were critically and audience acclaimed movies at the time of release.
William Holden and Kevin Costner are sometimes forgotten when westerns are discussed. You can find a quick rundown here. They both had other projects and key roles in their careers, but they were great western actors. Kevin Costner starred in Dances with Wolves and Silverado. Holden played key roles in The Wild Bunch and Texas. They will forever be remembered and cherished.