Starring in a western and being iconic are 2 different things and neither of these guys were good actors…
True, as for being a good actor................The absolute best actor on that list by far is Lee Marvin, & it's not even close with James Stewart probably 2nd.
John Wayne, at the top of the list, is iconic & a "tough guy" that lots of people liked to identify with, but as a talented actor, he probably at the very bottom of the list or even below. He had one style, & one style only.
As for a top western actor's list, Kirk Douglas surely belongs on it.
MM