I loved the Watchmen movie, and never read the graphic novel, although I hope to as soon as I can. I loved the realism and pessimistic feel of the movie, but it's a movie I had to watch twice to understand. I think it had way too many flashbacks, but I guess I wouldn't understand anything if they all weren't there. What I find funny is that Nite Owl went from a coward way too scared to get into a superhero suit to a cunning superhero screwing hot chicks in his superhero flying machine.
The thing is, if there was a sequel , it would be too predictable. If I put the Watchmen in any situation, we all know what would happen. That would be my only problem, other than everyone's favourite character being killed at the end of the first movie.
So by the end of the first movie, everyone is happy and standing in a circle holding hands, bobbing up and down to 'Happy Days', as they are surrounded by a comforting stampede of unicorns, purple squirrels and floating seahorses, all singing along with glee.
How can anyone start a movie with that situation? Well, maybe you could reserect Hitler and make him nuke all the people bobbing to 'HappyDays' but that destroys the realism, doesn't it?