Screenplay: Nicholas Pileggi & Martin Scorsese based on the book “Wise Guy: Life in a Mafia Family” by Nicholas Pileggi
It's actually difficult to explain how or why it's great these days. I guess the best way to look at is that, Scorsese's best films aren't based on plot. In fact, Scorsese argues that before "The Departed" he never actually made a movie with a plot. (Hmmm, I'm not sure I entirely agree with that, but I get what he's saying.) "Goodfellas" isn't about it's plot, it's about the feeling of being a gangster, basically in the same ways that "Raging Bull" was the feeling about being a boxer. (Or, well, really the feelings of being Jake LaMotta) Henry Hill grew up wanting to be a gangster and he got his wish, and despite everything, he absolutely loved it. Scorsese probably felt a little of the same way; he famously grew up a sickly child and often would look over out his window and watch the gangsters of his neighborhood. He'd made several movies about them before, most notably, "Mean Streets", but that was a movie that was still on the outside looking in as it looked at the actions of the street-level hoods. Henry is a street hood but not for very long. Despite being Irish, he's brought in by Paul Cicero (Paul Sorvino) the local beloved kingpin and he forms his own little crew with Jimmy Conway (Robert De Niro) and Tommy DeVito (Oscar-winner Joe Pesci). They rise in the family and enjoy living the lifestyle of being mobsters. They all enjoy it, although some enjoy it more then others. Tommy is a loose cannon who nobody can ever tell what's gonna snap him off or not. The most famous scene in the movie is where he damn-near frightens Henry, and all of us, just by questioning a claim that "He's funny." We love that scene, but it's interesting how it sets up some later scenes where he kills an unsuspecting waiter in a fairly similar situation.
It's always his actions that gets them in the most trouble, like when he kills a made guy who was unkillable and they have to bury him as oppose to just disposing of regular dead body any-old-where, but not before stopping by his Tommy's mother's (Catherine Scorsese, Martin's mother) house to eat dinner.