LazyAndroid: Ok, this is controversial.
It's not a post-apocalyptic setting, and I haven't even finished Fallout 1, but to me so far at least the mood is exactly the same:
Once upon a time in the west.
While this is more about the building of a new civilization and not so much about adapting to the fall of civilization, both are points of transitions between the old and new and share a same status quo. Of course they also share common elements, like the dessert, gunslingers, technology that doesn't work anymore/yet, etc.
And on top, it's a very good movie, even if you don't agree that it fits the mood.
DOES anyone agree?
I agree, totally. Fallout 1 & 2 definitely have owe a debt to the Dollars trilogy--Fo2 especially, those who've played it know what I mean ;)--and by extension to "Once upon a Time in the West". Furthermore, most RPG games owe a debt to Kurasawa's samurai movies (Jojimbo, Seven Samurai, Hidden Fortress). The stories you see in those movies lend themselves to RPG games very well: the superhero fighter comes in to save the day, repeat.
So, apart from the setting, the themes and narrative fall into line quite well.