The music is great. Perfectly fits the time period and setting, I dunno how much they had to pay in royalties for the songs in this film, but I love em'.
The camera work is fantastic. There's a scene where the camera gives you charlie's viewpoint, stumbling, wobbling across the bar, lights flashing, people dancing, music blaring, then zooms out to his smiling happy face. Then there's the filming of the street festival and the overall way which New York is captured so perfectly. It feels like you are really in the city, the movie has that gritty feeling to it.
The dialogue is great, many of it is ad libed by Deniro and Keitel. This is the beginning of ad libbed dialogue for deniro, the culmination being his speech in front of the mirror in taxi driver; "You talkin' to me"? There's a scene where Keitel confronts Deniro outside the bar to ask him about his debt, the exchange is perfect, it could never have been written and its executed beautifully.
The acting is also fantastic throughout.
So, great acting, great filmwork and great dialogue all come together to create a wonderfully realistic film.
Now, the end of the movie, maybe you didn't understand it, so I'll explain the film. I'll try not to spoil the ending.
Ok, so Charlie does some bad things, he works for the mob after all, and he wants to repent for his sins, so, after going to church and then later seeing jonny boy in a bar he thinks that God has asked him to repent for his sins on the streets, by helping out Jonny Boy. He doesn't believe that saying a few hail mary's or confessing washes away one's sins. So enter the walking train wreck that is Jonny Boy.
Now, what type of person is Jonny Boy? He has no sense of responsibility, he does not answer to anyone, he does not obey any rules, never does what is expected of him.
Hmm, so what type of person is Charlie? There are several scenes in the film that let you know what type of person charlie is. The statement Charlie loves everybody and everybody loves Charlie almost sums it up. Charlie wants to please everyone. But his life is full of conflict. You can't be in the mob and be religious, it just doesn't work that way. You can't hang out with guys who are racist and date an African American. These are just a few examples, but suffice to stay that Charlie wants everyone to like him, the local mob boss, his friends, his God, but he also wants to be happy and do the things he wants to do. There is conflict in all of this. Some of the other people that charlie wants to please, eg., God and the mob boss, have conflicting agendas. Some of the people that charlie wants to please conflict with what he personally wants to do with his life, eg. he is embarassed to be dating the epileptic because he thinks it shows weakness to his friends, but he loves her and she makes him happy.
You cannot please everyone. The irony of this film, and this is a little spoiler, is that while charlie is trying to save jonny boy, he should take a few lessons from him. Jonny Boy does whatever he wants without thinking about who he might upset, or disappoint. Charlie is the complete opposite. Yeah, Jonny Boy is destructive and his life is falling apart, but the point is that the two of them represent two opposite extremes. This is why the end of the film is tragic, its the lesson that you can't make everyone happy, that life is full of conflict, the conflict may be between different people in your life which you try to please, or between yourself and other people in your life. These basic conflicts and how we deal with them sum up who we are as human beings.
So there are many reasons why this film is great, I highly recommend giving it a second chance. I watch it every once in awhile and it really is one of my favorite films.