Honestly, who will watch the Watchmen? I'm sure Alan Moore would have an ironic chuckle at the superficial treatment of his work. That's not to say it's a train-wreck flop, but I do honestly wonder who it's supposed to appeal to and what the point was.
It sounds odd, but the film it reminds me of most is Daredevil- there is a playful narrative structure, a desire for a "darker" comic book film and a degree of campness that is either unwitting or woefully misjudged.
For those who don't know the plot, essentially someone is killing off superheroes and a gravelly voiced man in an ink blot mask (Rosarch) is investigating. The superheroes themselves are now retired (except the aforementioned tar gargler) and suffering various personal issues.
The problem is that things have come full circle- The Comedian looks too much like Robert Downey Jr, the issues of a double life have been better explored elsewhere, and Sin City has already provided us with gaudy, superficial shocks and violence. Granted, none of these film adaptations would exist without Watchmen's subversiveness, but it still feels like an ageing hipster trying to prove he's "with it".
And then we come to "visionary director" Zak Synder. What is clear is that he loves Watchmen, and tries his best to match it. But it's like a fairground caricaturist painting Mona Lisa- I'm sure he means well, but it's not the real thing. Now I'm sorry, but in my opinion the "visionary" tag belongs to people like Stanley Kubrick, David Lean or Orson Welles. Pretty pictures and ludicrously OTT violence doesn't make you an A-list director, nor does the vast sum of money a film might make (though in this case more likely from kids sneaking in).
If this sounds harsh, it's not because Watchmen is a bad film. The Dr Manhattan storyline is well handled, and adds some much needed pathos and tragedy to an otherwise superficial story. As Gilliam rightly predicted, the running time of a film doesn't allow sufficient room to breathe for the other characters, so we aren't give enough to sufficiently care about them.
In short, a good metaphor for the film is its soundtrack- for every clever use of Bob Dylan and Simon and Garfunkel, we get the ill-judged Leonard Cohen Hallelujah (a great song now sadly overexposed) or 99 Red Balloons. If you can forget the comic, if you don't mind excessive violence and slow motion and not that bothered about character development, by all means go and see it.