John Wayne may have had a bit of "sameness" in his roles, but he was billed that way. If one watches for the subtleties in his movements and expressions, it can be discovered that he was a great actor. He threw in humor very well, too.
He was better with age -- True Grit, The Shootist -- but he had some great early roles -- Stagecoach, Big Jim McLain, The Searchers, etc. -- for which he deserved more credit for his acting ability.