If Dexter would've been a movie

I'm not trying to take away the essence of the series, because I enjoyed it as well. But I was thinking, hypothetically speaking, what if Dexter would've been a movie instead of a TV show? Now I know that means the story would've been forced to be condensed, leaving out a lot of further plot continuations. But think about...what would that have been like? Maybe it could've been similar to an American Psycho.