Unlike "Children of Men", D9's bleak view on human nature is somewhat tempered by a more personable protagonist. The film begins documentary-style, then progresses into a more traditional action-film format while occasionally reverting to drive home subtle points.
Subtlety? In an action-sci-fi flick about aliens? The themes expressed in painful detail are greed and xenophobia, both masterfully set against the background of south African poverty. The parallels to apartheid are uncomfortably close to home, but the director Neill Blomkamp never preaches to his audience. There's no brute-force moral at the end of the film, and no public service announcement about 'love-thy-neighbor', but District 9 accomplishes two things rarely seen in a Hollywood summer blockbuster - it makes you think, and it's genuinely entertaining.
The first half may drag a bit, especially if one expects the movie shown in the trailers - full of gunfights and robotic alien exoskeletons. Don't give up on it. The scenes filmed in actual south african shanty towns are authentically filthy. The CG aliens blend perfectly with the environment, both due to rendering quality, cinematographic composition, and the director's skilled ability to treat the CG actors almost as human characters - not just digital artifacts.
District 9 definitely earns its R-rating with scenes of gore and brutal violence. While some might feel it unnecessary, I felt myself genuinely unnerved by some of the scenes - both the body-horror moments of inhuman transformation, the agonizing pain of torture, and the disturbingly real portrayal of violence against the aliens - scenes that play out against humans on the nightly news. There is vomit, gore, cannibalism, alien dissection, gunshot executions... but it's never done to impress, only to convey the reality and deadly seriousness of this film.
Not to say that it's a boring piece of work. Despite its brutal themes we see a wide spectrum of emotion - both human and inhuman - that somehow never feels out-of-place. There are laughs among the horrors, touching moments are found in between moments of nauseating violence, and real romantic feeling hidden behind intolerable cruelty. In one film, we cover the highest and lowest peaks of feeling, and it's never fake. This is the power of good cinema - to take the truth of human existence and distill it into a tale that resonates with every sentient being.
You will feel bad by the end of the movie. You will think deeply. You will cheer the protagonists, and thrill at the well-choreographed action, but you will trade in a bit of your faith in humanity. Neat gadgets abound within a fully realized world, but at its core District 9 represents the purest purpose of science fiction - exploring a future that hasn't happened yet, based on where we are right now. There are very real situations exactly like this film, being played out in third world countries all across this globe, and if a science fiction film about aliens opens people's eyes, then Neill Blomkamp and Peter Jackson deserve far more recognition than simple box office gross.
District 9 is an impressive film by Hollywood standards, but by human standards, it's a work of art. Don't let the exploding people, cool alien weaponry, and intense firefights distract you from the true message of this film - we treat humans as badly, or worse, than the aliens of District 9 - with an equal amount of greed, exploitation, xenophobia, and contempt.