High Noon is a great film, but it shouldn't be on that list as it isn't a western, but a political thriller.
Well, if you're going to discard it, there's probably a few others on there that don't belong. Considering what it's about, you could also argue Treasure of the Sierra Madre doesn't belong either.
It's a really widely stretched genre, fitting in more sub-genres than maybe any other.
Overall, I thought the list was OK. Had all the obvious choices, and a few interesting ones (McCabe and Mrs. Miller doesn't get mentioned that often).