"Watchmen" is widely regarded to have brought an aura of realism to comics.
I think that more often it's a more supposed physical realism rather than any kind of emotional realism. Yes, books like "Watchmen" did make it fashionable to show grimly the consequences of violence, which I suppose initially was a good thing because it's better that people know that violence results in terrible injury and pain and suffering than that they think that it's just something that, you know, people get a sock on the jaw and they are unconscious for a couple minutes and then they come around and they are taken off to the police station.
But I think that when you are talking realism in comics you have to realize it's an ongoing process, especially emotional realism. That when the comic book industry started you had characters who were, let us say, one-dimensional in that they only had one quality. They were good or that they were bad. By the 1960s Stan Lee with Marvel Comics had the brilliant idea of two-dimensional characterization where they are still good or bad but now they have some kind of, perhaps a medical complaint or some sort of emotional suffering. What we were trying to do with "Watchmen" was to make it at least three-dimensional. So that the characters that we were talking about were complex human beings that weren't defined by one simple set of behavior patterns. With some things like Todd McFarlane's "Spawn" or a lot of these modern comics, they will show greater violence because they know that actually that is what a lot of the audience wants, for prurient reasons, not trying to show the emotional depth and complexity of the characters.
It's occured to me that many of the characters I've seen in various fiction are incapable of growth or change. A character is concieved as a brand with a certain set of unchangable characteristics that can be exploited by the narrative again and again and again. Consider the simpsons, and their world which resets at the end of each episode to exactly the way it was at the start. None of the characters get older, nor do they actualy learn anything from their adventures that modifies their future behavior, or makes them quantifiably better people.
How would a fictional character look, if it was capable of growing and learning? What if in the process of that growth, they abandoned the main attribute that made them recognizable as that character, and that change persisted to future stories? Is emotional growth the third dimension Alan Moore speaks of?