Since the comic was ground-breaking in its original portrayal of superheroes, the movie can't live up to that since it's as close a literal translation as one could imagine.
It's ground-breaking for superhero movies in that regard, but not nearly as much as the comic was. In terms of film, it's a lot more violent and ambiguous than most superhero movies, although its box office performance will be a more important factor in its influence on the genre, rather than the fact it exists at all. I mean sure, you can put in as much violence as you want, but if it doesn't equal more business, it won't catch on.
Also, even though the plot of the Watchmen comic is fairly simple, the world it portrays and the structure of the storytelling are the things that made it timeless. Snyder succeeded in the first point, but only a virtuoso structure-based storyteller could have handled the second. I felt the genius of the comic's structure was lost in the movie, and I don't know if simply inserting Tales of the Black Freighter will make it up.
Ironically, I think Nolan would have been the most appropriate writer/director to give more oomph to the structure, even though I expect he would have stripped the story down to its bones and then built it back up, like they did for The Prestige.
I guess it's all comes down to which part of Watchmen you want to emphasize. In terms of look, it really couldn't have been done better. In terms of story, it's a lesson that following a compelling comic panel-for-panel doesn't mean a film will be as equally compelling.