What I always thought made Watchmen so spectacular was that it held up a mirror, clear and brutal, to the often blithe mythology of superheros, in two ways. First, it took what Marvel started in the 1960s, with superheros as people with real problems, to its most logical extension.  Rather than simply being human beings who incidentally wore masks and had outrageous abilities, Watchmen probed what kind of person would decide to put on a mask in the first place, and whether or not Spiderman's Shakespearean couplet that:

With great power
comes great responsibility

might actually lead to, at best, a certain narcissism, and a worst, a megalomania or even a dehumanizing God-complex. In Moore's mirror, putting on a mask doesn't just protect an identity, it builds a wall against the world, and allows any basic human neuroses, normally worked out in the day-to-day of being around other people and communicating, to fester and grow.

But Watchmen also moved outward from the psychological to the social, outlining an alternate history of the 20th century injected with costumed neurotics.  In so doing, Watchmen went beyond the insulated societies that populated most comics, and into a powerful critique of comics themselves. What about our society requires superhero mythology?  Does it say something about us that we value these people in costumes as a form of entertainment?  Given a society as contradictory and dangerous as ours, might superheros be too simple a solution to problems that we face?

This made Watchmen almost necessarily reactionary, because it described a world like our own and then used that description as a critique. That world, of Cold War state and personal terror, rampant consumerism combined with merciless monopoly capitalism, widespread inequality, and fragmenting identity became more than a backdrop for Moore's tragic narrative about costumes and masks--it was a character unto itself, perhaps even more powerful than Dr. Manhattan.  Watchmen was of a time and place, and more than anything else, it felt urgent in its desire to wring every ounce of meaning and sanity from a world increasingly meaningless and insane.

And it's that element that is not present in the film adaptation.  But how could it be?  For Zack Snyder to have made a "true" adaptation, he would have had to change the setting and the story to something more closely resembling our world; he seems too much of a purist to let that happen.  And he would have had to make a deliberately political and polemical film, which would have upset studios already strained with drying budgets, lawsuits, and nearly 20 years of attempts and failures to get this film to screen.  What we have instead feels like a period piece, with its subtle fury almost quaint, and safely nestled in the past.