So, what system would you use and specifically, what element of that system would best serve to support the setting and tropes of the story?

I'll throw down the first glove and say it out loud. Watchmen is all about the character interaction, not the superheroics. It'd be best served by a narrative system that emphasises the personalities of the characters and how they affect their abilities. My suggestion out of the gate is: HeroQuest. Personalities and relationships can be used to modify abilities, or can be used as the primary abilities themselves.

!i!

I'm with Ian on the diagnosis. Except I never liked HQ, so I'll suggest Truth & Justice as the cure

PDQ's descriptive mechanics, it's going to do wonders for that type of game.

Capes. The Heroic Drives work well for the Watchmen:

Truth is obviously a big thing for both Rorschach and Silk Spectre II. Love is big for both Silk Spectre II and Night Owl. Duty comes into several of the character's stories, and Hope (for Capes, "How much the hero's story revolves around the safety, needs, and doubts of the common man") is big for Dr. Manhattan, through his disconnection from humanity.

Ozymandias and The Comedian each exemplify some of the villainous drives -- for Ozymandias, Pride and Obsession; for The Comedian, Power and Despair. Since Capes allows mixing heroic and villainous drives, crating these two as "hero-villains" is no problem.

Others mentioned personality as more important than powers, and that comes in here as well. You can easily build characters that depend more on Capes' Attitudes and Styles than Powers.

Further, Capes' system is perfectly built to handle goals like "Persuade Dr. Manhattan to return to Earth", and its Events allow for things like "Silk Spectre realizes that The Comedian was her father" to be points in game play.

I wouldn't want to play The Watchmen. Though the world is cool, I'd feel too much like I'm constantly trying to chase the themes and narratives of the comic. That said, I'd probably play it totally straight using GURPS (if I still had the patience to work with complex systems).

My suggestion for Watchmen is: start with the basis of Moore was trying to do and go from there. Forget the specific application (which is, after all, stuck in the 80s). What happens when you try and reimagine superheroes from the ground up?

Unknown Armies, with its Passions and its Madness Meter, might make an interesting choice for a Watchmen game system.

Hmm. And, with the notable exception of Dr. Manhattan, all of the heroes are peak-level-human, not super-powered. That could prove interesting.

!i!

And even Dr. Manhattan failed his hardened roll, when they presented him with his cancer-ridden first wife.

It is an interesting suggestion. I think some tweaking would be in order, but the basic idea is quite interesting.

Virtually all of the major character moments involve said character blowing a stress check, now that you mention it.