The Western genre has more theatrical titles than any other (horror has more titles now, but so many are straight to video ones, so I'm just considering movies in a genre that have played in a theatre).
Below are my 20 all-time favorite films from the Naro's Western section or from individual director shelves as moted:
1. The Man Who Shot Liberty Valance (on the John Ford shelf)
2. Once Upon a Time in the West
3. The Ox-bow Incident (William Wellman)
4. The Wild Bunch (Sam Peckinpah)
5. McCabe and Mrs. Miller (Robert Altman)
6. My Darling Clementine (Ford)
7. The Good, the Bad and the Ugly
8. The Magnificant Seven
9. The Outlan Josey Wales (Clint Eastwood)
10. Unforgiven (Eastwood)
11. Will Penny
12. The Great Northfield, Minnesota Raid
13. Stagecoach - esp. the Criterion edition (Ford)
14. 3:10 to Yuma (both movies)
15. The Naked Spur (Anthony Mann)
16. High Noon (Fred Zinneman)
17. The Ballad of Cable Hogue (Peckinpah)
18. Dances with Wolves
19. The Professionals
20. Ride the High Country (Peckinpah)