It is The Future. The world has been all-but consumed as a result of an endless war, with the wasteland dotted with heavily fortified urban metropoli, ruled by an all-powerful totalitarian state. It could be Judge Dredd, but it's not. It's Priest.
In this case, the all-powerful totalitarian state is The Church, who are getting away with this, because the endless war in question is against Vampires. It's been a pretty even fight between humans and vampires throughout history, because while the vampires are faster and stronger, we have all the cool advantages that being a tool-using species, and being able to go out in sunlight entail. This stalemate position was eventually broken, however, when The Church unveiled their ultimate weapon - Priests. Sadly, this does not mean that the war was won by signs reading "Down With This Sort Of Thing" and "Careful Now." It means that Priests are highly trained martial artists and hand to hand warriors, trained in the art of taking on vampires in combat. (All this comes from a Japanese manga originally, and according to some, is a deliberate misreading of Christian religion which parallels Western misrepresentation of Japanese culture. Fun.)
Anyhow, the Priests won the war, and were then disbanded, because for some reason the totalitarian state couldn't think of a reason to keep on a squad of fanatically loyal super-warriors. So the priests get by on menial jobs, until one day a sheriff from the badlands outside the city comes to find one of these ex-Priests (Paul Bettany), to tell him that the vampires are back, and have kidnapped his niece. He wants to go rescue her, the Church won't let him, because that would mean admitting that there was a vampire problem, he goes anyway, and the church bring some more priests out of retirement to hunt him down for breaking his vows of obedience. Game On.
All else is your standard plot of a posse following a trail to hunt down the bad guys and rescue the girl. The film is not so much riddled with cliches in the same way as a house cannot be said to be riddled with bricks. The cliches are the film, are part of the construction of the film, and nothing good about the film could exist without them. It's part Western (with the posse whizzing around the wild west desert on jetbikes), part post-apocalypse sci-fi, and part alien bug-hunt. And I say bug hunt, because these aren't boring shiny Twilight vampires. Nosiree. These are big hissing eyeless alien creatures more reminiscent of xenomorphs from Alien, with the power levels dialled down a little so that it's mildly feasible that a human could survive an encounter with them if he's very, very skilled. And fortunately, they are very skilled, with Paul Bettany and Maggie Q (as a Priestess) being in possession of some serious crowning moments of awesome.
I'm not sure everyone will like this movie. If you can't bear a cliche, then stay away. If, however, you enjoy watching the conventions of genre being *rigidly* observed, as I do, then you'll enjoy it. Atmosphere wise, well, you can go Fun, you can go Serious, or you can go So Damned Serious, It's Funny. In my view, it's the latter. Paul Bettany wanders about the place being all gloomy and portentious the whole time, and it's stupidly over the top. Bad bits? Well, Karl Urban, as the big bad guy, is saddled with some awful dialogue. And the Sheriff sidekick, Snoozy McFallsdownalot, is so tragically inept in comparison with The Priest, that you almost have to wonder why he's there at all.
A final point - the 3D, slapped right there in the title, is either poor or nonexistent throughout. I don't know if they're distributing it in 2D at all, but if they do, that's probably the better option. Again.