I think the comparison to Bethesda and Fallout 3 is a more than apt one.
First off, because there is no need whatsoever to turn it into a movie, just like there wasn't to making Fallout 3 FP and RT - it is as much a product of a creatively bankrupt industry as our beloved sequel. Exactly like Tim Cain and co. aimed to replicate the PnP experience, Moore intended to explore the inherent characteristics of comics as a medium. Quoth the man,
Alan Moore said:
You get people saying, 'Oh, yes, Watchmen is very cinematic,' when actually it's not. It's almost the exact opposite of cinematic. [...] I didn't design it to show off the similarities between cinema and comics, which are there, but in my opinion are fairly unremarkable. It was designed to show off the things that comics could do that cinema and literature couldn't.
It also happened that Watchmen was no longer under creative control of its authors when the rights (to the movie, in this case) were sold off to Big Business corporations who couldn't give a damn about anything beyond sales figures. Sounds familiar?
Just like Bethesda, Zack Snyder is good at fluff, and worth shit for substance. Anyone happen to see 300 and his Captain America Leonidas? The convenient removal of his "this is not a democracy" line to Stelios, for an instance? He deems it something for athenians, whom he previously referred to as "boy-lovers", but in the movie version we get a sanitized character for imbecilic audiences who can't recognize heroism outside their own political values, hence also the "hurr, I'd die for my soldiers" speech. Same for Queen Strong Independent Woman Gorgo - feminism in ancient Sparta, ahoy. Snyder captures visuals quite well, but the instant the story goes against shareholders' perception of the market's sensibilities, out the window it goes.
How can one say Snyder has any respect for the work when he deems his skewed version of things better and changes dialogue and story like dirty underwear? We now have, for an instance, a group that was actually called "The Watchmen". A lot of the changes you hear about on the internet are incredibly stupid and ham-fisted, the ending ends up being the least of the problems.