I am critically ignorant when it comes to Westerns & am very, very new to the genre. Two years ago, the only "Westerns" I had seen were the Young Guns type of stuff. Tombstone too. Some friends whetted my curiosity & made me realise that I might be missing out on something special. So I got some recommendations & started watching some of the classics, mostly from the 70s. I was surprised at how much I enjoyed many of them.
My favourites so far:
High Plains Drifter
The Good, the Bad, & the Ugly
Unforgiven
The Assassination of Jesse James by the Coward Robert Ford
Open Range
I realise that including the more modern films is anathema to huge fans of the genre, but Im still getting my feet wet, really.
Others I liked a lot are:
Two Mules for Sister Sara (any Eastwood Western worked out well for me)
McCabe & Mrs Miller
Jeremiah Johnson
Wyatt Earp
Once Upon A Time in the West
Anyway, I got some good recommendations from reading through this thread, so I will continue to watch & learn.