First real crime movie?
I think people do not get the significance of this movie as there are plenty of posts that are insulting this movie.
Nowadays when people think about great crime movies they say Goodfellas, Scarface, Pulp Fiction, The Departed etc. Back before this movie came out crime movies consisted of hard-boiled detectives with a top hat trying to solve a crime while romancing a 'dame'. This movie changed that by showing a completely flawed and vulnerable character in a mob-enforced environment. As a result it changed the flow of crime dramas that came out. Sure the violence and language is tame by today's standards but I still hold this as the yardstick when it comes to this genre.
In fact I would go on to say that this is the greatest American crime-movie ever made. For those of you who didn't like this movie please watch it again. I assure you I started to love it after my third viewing.