It seems like sometimes it's best to look at who makes them more that what were the best.
Tom Selleck made some great ones, such as Crossfire Trail and Last Stand at Saber River. Horse Soldiers was a fantastic western. So was Ron Howard's version of The Alamo. I s'pect we could list these all night.
I love the Tom Selleck westerns. Those led me to his Jesse Stone series and finally to Blue Bloods.