The Road really is an empty movie in most parts, with a empty ending out of what is a heartbreaking scenario. How they made that film into something so devoid of emotion is beyond me.
Children of Men is great, the overall vision of the future represented in it is believable and interesting, although it is not post apocalyptic, it is set a period which we assume is approaching an apocalypse of some kind (although it's interesting that our definition of an apocalypse is centered around the human species being eliminated).
I'll have to check out some of the others named in this thread, because most of the films i've seen from the genre have been pretty poor.
I tried to hold back from ranting about V for Vendetta, but it is such a facile film. If you can divine any kind of philosophical or political meaning from that you should move into alchemy.