The 'Outlaw Josey Wales' is my all-time favorite movie period! But I do not consider it a western. After all , most happened in Kansas and Missouri.
And since not one of the classsic old time westerns really distinguishes itself in my mind , I'll vote for a fairly recent one in 'Silverado'.
Classic 'western' story line (good guys v bad guys)
All-star cast
Technically accurate for the time
Period correct firearms
Timely humor
Plenty of shootin' , fightin' , rustlin' , drinkin' , gamblin' , cheatin' , lyin' , and shootin'!