Here's the Top 10 of All Time.
Don't try to deny it.
1) Butch Cassidy and the Sundance Kid
2) Big Jake
3) Tombstone
4) Undefeated
5) Unforgiven
6) The Man who shot Liberty Valence
7) Support your Local Sheriff
8) True Grit
9) Young Guns
10) Sons of Katie Elder
I went with Unforgiven. I just watched it again the other day. There are a lot of great ones on that list though and some great ones that aren't... The Wild Bunch, Red River.... Stagecoach ?
I went with Unforgiven because it was one of the few Westerns that didn't over-saturate violence. It starts slow and then comes to one badass, drunken climax.
I chose The Outlaw Josey Wales because it is my favorite but The Good, The Bad & The Ugly would be worthy just the same IMO.
Lee Van Cleef is one of my favorites of all-time! He is a huge part of why I like Westerns. That Star Wars CGI show even has a bounty hunter based on LVC.
I haven't seen a lot of the classics but I picked Unforgiven.
I'm also a big fan of both Young Guns movies, especially the 1st. They're never in contention for best western but they can sometimes find their way onto a few people's Top 10 lists, as they did in this thread.
I also really liked The Assassination of Jesse James by the Coward Robert Ford, even if the title is the biggest spoiler ever. Not your typical western as there isn't much action and it's a lot slower than most but a great movie in my opinion.