IGN, in a 5.10 article, posted their Top 25 Westerns of All-Time as a tie-in to the video-game release of Rockstar's Red Dead Redemption.
Considering the source (not that IGN is a bad site, but at the end of the day, it caters to a large, young video-game/fanboy demo), it isn't a bad list at all. A bit too populist and a bit too modern, it nevertheless will suffice as a decent list. Here goes:
1. Once Upon a Time in the West (Sergio Leone; 1968)
2. Unforgiven (Clint Eastwood; 1992)
3. High Noon (Fred Zinneman; 1952)
4. Shane (George Stevens; 1953)
5. The Wild Bunch (Sam Peckinpah; 1969)
6. The Searchers (John Ford; 1956)
7. The Good, The Bad and the Ugly (Sergio Leone; 1966)
8. Butch Cassidy and the Sundance Kid (George Roy Hill; 1969)
9. The Magnificent Seven (John Sturges; 1960)
10. The Man Who Shot Liberty Valance (John Ford; 1962)
11. Rio Bravo (Howard Hawks; 1959)
12. The Outlaw Josey Wales (Clint Eastwood; 1976)
13. My Darling Clementine (John Ford; 1946)
14. Tombstone (George P. Cosmotos; 1993)
15. The Professionals (Richard Brooks; 1966)
16. 3:10 to Yuma (James Mangold; 2007)
17. McCabe and Mrs. Miller (Robert Altman; 1971)
18. The Naked Spur (Anthony Mann; 1952)
19. Will Penny (Tom Gries; 1968)
20. Pat Garrett & Billy the Kid (Sam Peckinpah; 1973)
21. A Fistful of Dollars (Sergio Leone; 1964)
22. The Gunfighter (Henry King; 1950)
23. Silverado (Lawrence Kasdan; 1985)
24. Little Big Man (Arthur Penn; 1970)
25. The Treasure of the Sierra Madre (John Huston; 1948)
The biggest problem first off is the egregious praise given to two of John Ford's most overpraised westerns (Liberty Valance and The Searchers) while neglecting two of his best: Stagecoach ('39) and Fort Apache ('48).
Secondly, there isn't nearly enough Anthony Mann, with The Far Country ('55) and The Tin Star ('57) noticeably absent alongside the similarly neglected Robert Aldrich's Vera Cruz ('54).
I also look forward to the day when George Stevens' Shane ('53) is rightfully removed from Top 10 vicinity so that kid can stop shouting his name. And The Magnificent Seven is actually pretty good, but it loses major points for just stealing the plot of Akira Kurosawa's Seven Samurai and not capitalizing more thoroughly on one of the greatest western casts ever assembled.
And lastly, I've always thought that Sam Peckinpah's Pat Garrett & Billy the Kid ('73) was his masterpiece, not The Wild Bunch ('69). I need to do a western list myself, but I still have so much lesser-known stuff to see to accurately compile it, so I'll hold off for now.