Best Western?
No doubt Silverado! Great music, great story!
I will also nominate Rio Bravo, Fist full of Dollars as well.
Although not best western "ever", - 3:10 to Yuma, last year's remake with Russell Crowe and Christian Bale, was the best western I've seen in a long time. Although most of what I read about Crowe makes him seem like a jerk, the guy can act.