If the source material for Watchmen didn’t exist, I think everyone would be a lot more well-disposed toward it, as Alan Moore came up with a great story that Snyder mostly keeps intact. That said, the source material does exist, and it’s hard not to notice that, almost every time Moore’s comic makes the material drab, or sad, or mundane, Snyder injects cinematic steroids into the moment to make it flashy, or edgy, or badass. He’s clearly uncomfortable with the idea of showing superheroes enter a sad, anonymous decline in a world they have made definitively worse, which was one of the central points of Moore’s story. The list of changes from the comic to the movie is basically a catalogue of Snyder’s shortcomings as a director of movies and a reader of comics.
Then again, I was personally incensed to find that nobody here listed Spider-Man 2 or the original Superman among their favorite comic book movies, so I think Snyder is generally selling something a little different than what I’m buying.