As much as I wanted to vote for one of the BEST Movies EVER on celluiod- to wit; "The Magnificent Seven" !!! But since it takes place in a village ..."a couple days ride south of the Border..." It would actually be a "southern", rather than a "Western".
I voted "Other". The Greatest Western flick... would probably have to be one that covers "The Westward" movement.
It would have boats, rafts, canoes, wagons, buckboards, Rifles, Pistols, lances, Bows/arrows, Pioneers, Fur Trappers/fur traders, Indians, Soldiers, Locomotives and tracks and Track Layers, Cowboys, Gamblers, God-fearin' folk and saloon/show people, funerals and graves, and marriages and children, Criminals, Lawmen, Miners, Businessmen, Pony Express Riders, telegraph poles, buffalo herds. Therefore, I nominate:
"How The West Was Won".