First and foremost, “Watchmen” was the first of its kind. It stood out from the crowd in an exemplary fashion. It put other comic books to shame. The writer, Alan Moore, took a more non-traditional approach to writing it. For starters, the storyline doesn’t take place in a fictional city like most other comics do. It takes place in New York city. Also, this story was portrayed as more realistic. While it is still loaded with physical impossibilities, the comic had a more real feel to it due to its setting, timeline, and character personalities. You would also find that the Watchmen graphic novel didn’t look like it fit in on a typical comic rack. The front cover would seem much more boring than that of a traditional comic book. These factors definitely made it unique.
https://screenrant.com/how-watchmen-changed-comic-books-forever/#11-cold-war-commentary
It’s been several years since I have seen the 2009 film adaptation, but I do remember owning it when I was a kid. I can recall the first time I watched it and what my reaction to it was. I could tell right from the beginning that something about this superhero story was vastly different from any other superhero story I had ever seen or read before that. There was just something about how it was filmed that made all other superhero movies seem like corny fiction but this, this was real.
https://www.vox.com/2019/10/18/20917361/watchmen-hbo-comic-superheroes-explained
This work of art was certainly one of a kind and I am still waiting to see something that tops it.