I'd call myself a fan of post-apocalyptic fiction, but it's wearing a bit thin lately. The format is pretty simple: Something destroys human civilisation as we know it, including most of the humans, and then the survivors have to rebuild somehow. The beauty of it, for me, is that it lets us dissect society and play around with the norms we'd otherwise take for granted, at least as much as speculative fiction allows.
Sometimes it's nukes that get us (as in Mad Max or Fallout), sometimes it's nature (Waterworld or that more recent global warming movie I never saw), frequently in the last few years it's been zombies (way too many fucking zombies!) and at least once it was dragons (in the not at all original, yet still oddly unique Reign of Fire), but the structure is seldom very different: Either the disaster has just happened (which gives some overlap with more conventional disaster movies) and there's a mad panic to survive one minute at a time with social dynamics changing drastically with every new character to suddenly appear or suddenly die horrifically; or it's a disaster that happened long ago, and we get to see the conflict(s) inherent in the new societies that have emerged from the ruins, with battles playing out on a grander scale over longer periods.
So the basic plot structure is fairly predictable, but that's not what bothers me. What bothers me is that too often nothing interesting is done with it. Perhaps it's because my first serious scifi was all Isaac Asimov, but I sort of expect speculative fiction to speculate a bit beyond the bleeding obvious. We can all assume that if a zombie plague starts spreading that people would get crazy and bad things would happen. But what does this tell us about humanity and society and shit?
Compare (with vague spoilers) the Will Smith movie, I Am Legend, with the comic (and now also vid series), The Walking Dead. In the former, the lesson is that Will Smith makes zombies and then has a shit time unmaking them, so... science is bad or good or Fresh or something? Nothing more profound than that. In the latter, we get to see all sorts of different things: Betrayal, stupidity, courage, selfishness, selflessness, complete insanity. And, more interestingly, all of this leads to an amazing variety of different outlooks and approaches to the situation, reflecting very well the reality of human society. A friend of mine complained that he found a few scenes in Walking Dead to be superfluously gratuitous, but I think that misses the point: These scenes were entirely within the normal (if uncommon) range of human behaviour, and Kirkman would have been remiss to gloss over them just because they're unpleasant. If we don't like what we see in the post-apocalyptic mirror, then it's not the fault of the apocalypse, but of our own real, present human failings. That's the point.
(You might complain that it's unfair to compare a movie plot, with only 90 minutes to fill, with an ongoing comic series that has way more time to expand on minor points or add wholly new things. In that case, I encourage you to read the original 1950s book, I Am Legend. They could easily have kept it more or less the same, and yet the original ending is far more profound even than the best parts of Walking Dead.)
But back to that point: Dissecting society with nukes or zombies or whatever is not only fun in a kicking down sandcastles way, but it also shows us things about ourselves. Mad Max 2 (clearly the best of that trilogy) shows us how reliant we are on the power we wield over each other and how we all abuse that power; the villagers with their monopoly of the only available oil and the raiders with their more direct physical violence. Dawn of the Dead (both remake and original) messes with all sorts of quirks of individual psychology, which under normal circumstances probably wouldn't be more than annoyances, but which are thrown into vivid clarity in a major crisis. Battlestar Galactica takes a different approach in each incarnation: The original was fun in several ways, but was rubbish as a post-apocalypse story as hardly anyone seems to care that all 12 of their homeworlds have been wiped out (possibly because they're in a galaxy crawling with lovely human colonies around every other star, making the quest for Earth seem a bit pointless), while the new series hits it really well, exploring several angles (including the idea of the shitty compromise colony that all the Mad Max clones always assume survivors would be perfectly content to occupy indefinitely). Even light-hearted post-apoc stories can act as interesting dissection mirrors (weird mixed metaphor there). Shaun of the Dead twists the Dawn of the Dead amplification of individual quirks even further, showing us how even incredibly mundane behaviour, taken out of its normal context, is far more odd than we tend to treat it. Zombieland also does a surprisingly good job of picking apart our entertainment norms.
I'm not suggesting that all post-apoc fiction should be written by PhDs in psychology and sociology; this is still art, not science. But good art, I'm told, should make you think, even if (or especially if) it can't provide the answer itself. And too much of the time I'm finding I'm not even being asked to think anymore. The post-nuclear sub-genre is now full of Mad Max clones which all assume that anyone left alive has to be either be a harmless, helpless peasant in need of Our Hero™, or a vile, evil raider who can't possibly be reasoned with and who only deserves to be killed by Our Hero™. The Book of Eli is perhaps the worst offender of that sort, blatantly copying the look of Fallout 3 almost exactly, but with even more 2-dimensional characters (even the personality-free blank slate who is the player-protagonist gets more depth in the opening 15 minutes of the game than Eli gets in the whole movie) and a pretty lame conclusion. And zombies... well, they're just a blurry cultural thing now, not even a genre or sub-genre, just some brain-eatin' self-referential joke.
Now, it could be that there have always been bad examples of post-apoc fiction, and I simply only know of the newer ones because nobody kept the old ones in circulation (a completely valid argument in the case of good vs. bad music back in the old days), but I think there has definitely been an increase in production of this stuff over the last decade or so, and the percentage quality yield has declined as a direct result.
I fell into the same trap myself, trying to run a game of Fallout P'n'P roleplaying set here in Joburg (and I went in with a great technical understanding of the subject, having published academic work on weapons of mass destruction), so I know how hard it is to really think deeply about these things and produce something either original or clever, let alone both. But if you are writing something post-apocalyptic, I encourage you to push yourself and consider what you want your audience to see in the mirror you're creating for them. What you do from there is your own business (that's how creativity works, right?), but please at least try to be aware of it.
[My friend Jamie, budding novelist and great 3D animator/graphic designer (available for hire, very reasonable rates), has pointed out a major, major point that I knew but completely left out: This post-apocalyptic mirror doesn't only show us the bad, but also quite clearly the good. The heroes' actions remind us of the good things we're capable of, and the different visions the survivors have for their rebuilt worlds reflect what they (i.e. we) find important and worthwhile in life. Of course, that doesn't have to be purely positive; the conflicts between individuals or factions in these stories reflect our similar real world inability to have all of our contradictory hopes and dreams fulfilled simultaneously. This may be partly why I disliked the conclusion of Book of Eli so much: Even if we accept Eli's vision of what'll make the world better as legitimate and not a cheap cop-out of a "twist" ending, then it's still one that I find personally very disagreeable.]