Many people compare "Once Upon a Time in America" with "The Godfather". In my opinion these two movies can't be compared. Both are masterpieces in their own way, but each of them has a different style. You don't compare a Picasso to Michelangelo's Sixteen Chapel either, do you?
What is it that makes this movie a masterpiece? Well, first of all there is the director. Sergio Leone is a real master when it comes to creating a special atmosphere, full of mystery, surprises and drama... He's one of the few directors who understands the art of cutting a movie in such a way that you stay focused until the end.
The way the movie was cut is also the reason why a lot of Americans don't think this movie is very special. There are three versions, but only the European version is how the director imagined it to be. He didn't want his movie to be shown in chronological order (1910's - 1930's - 1960's), but wanted to mix these three periods of time. The studio cut the movie in chronological order, loosing a lot of its originality and therefor getting a lot of bad critics. If you want to see this film the way Sergio Leone saw it, you have to make sure you get the director's cut.
The second reason why this movie is so great is the music. Ennio Morricone, who is seen as the greatest writer of film music ever, did an excellent job. Together with the images, the music speaks for itself in this movie. From time to time there isn't said a word, but the music and the images on their own tell the story. He understood perfectly what Sergio Leone wanted and composed most of the music even before the movie was shot.
Last but not least there is also the acting and the script. The actors all did an excellent job. But what else can you expect from actors like Robert De Niro, Joe Pesci... They helped making this movie as great as it is by putting there best effort in it. The script helped them with it. It took twelve years to complete, but it hasn't left any detail untouched. The writers really thought of everything when creating it.
I can really recommend this movie to everyone, but especially to people who like the gangster genre. When you want to see the movie, you better be sure that you will have the time for it. This isn't a movie that is finished after 90 minutes. You'll have to be able to stay focused during 3 hours and 47 minutes, which will certainly not be easy during the first 20 to 30 minutes. Some scenes at the beginning only make sense when you have seen the end of the movie. But when you are able to stay focused, you'll find this one of the best movies you've ever seen. I certainly did and I rewarded it with a well deserved 10/10.