I've heard some comparisons to the Blade Runner. I'll accept that to a point. Both are Film Noir, both are set in a dismal near future, both provided settings that are dark, dirty, and littered with garbage. I'm not sure I can come up with any other good comparisions.
Anyway, back to Children of Men. This was a movie that lets you know right away what kind of world it was set in. There was a coffee house bombing at the beginning after which a woman staggered out of the dust holding her severed arm. Wow. Did they really just do that to open the film? Yes, yes they did and it set a mood.
There was an urban combat scene, near the end of the film that was amazing and filmed in one long continuous take! Chaotic, random, violent. I mean come on -- tanks firing on buildings at point blank range while infantry shoots it out with snipers in the same buildings. I was on the edge of my seat. It was so well filmed that it felt like being there.
A big thumbs up to Children of Men as a modern and acceptable version of Film Noir.