The one thing Watchmen is not is a Superman movie. Thankfully. There have been no shortage of superhero or super-team films in recent years and some have even been quite enjoyable or inventive, but this is a different kettle of fish.
I am reviewing Watchmen as a film having (deliberately) not yet read the graphic novel. This is the opposite of most of the superhero mythos. So there's no battle of extremes - this is the first film I've seen for a while that sees good and evil as two ends of a spectrum and places each character, believably and consistently, in a different place along it, and there's a real confusion of the nature of heroes and villains. A few superhero movie traits survive the carnage - there are gadgets, exaggerated fight scenes and silly costumes, and the obligatory aerial vehicle. The ending, despite featuring a showdown with a supervillain in his hi-tech hideaway, is still resolved in an unsettling way that doesn't provide easy salvation. Instead there's a hero who's also a villain who does something quite naughty, but with good intentions, leading to a good outcome but with a high cost, and this seems to be a bit confusing for the simple vigilantes too.
And there's the tone. No superpowers except for Dr. M, and just a few surreal touches like Rorschach's ever-changing face. Adult themes. Nudity. Sex - one round of sci-fi, silly sex but also some suprisingly tender scenes later on. People die. A lot. With or without buckets of blood. Like I said, this isn't Superman.
Several ideas recur. Superheroes are a reflection of the society that creates them - the Comedian is a parody of the worst of humanity, a drunk murderous rapist, while Rorschach is of course whatever you project onto him. Becoming more powerful and identifying less with society - this is true of all the masked heroes although some are more irresponsible than others, and on a larger scale Dr. Manhattan's power genuinely makes him more and more inhuman.
The star of the show is loveable vigilante psychopath Rorshach, and in particular his voice which will be remembered in future times along with the likes of Darth Vader and Cookie Monster.