Sheer genius of everything. From the casting, to the screenplay, to the plot progression, to character development. Simply genius.
Not many movies now are about the gangster pop culture, and even less are about real life crime figures. The movie portrays the real life American gangster >Frank Lucas, of Vietnam drug-smuggling legend. He was portrayed by Denzel Washington, who I consider as one of the best ever actors in modern film. His portrayal of Frank Lucas was incredible, down to the swagger of his walk. His co-star is the equally brilliant Russell Crowe of Gladiator fame. Put those together, and with a director like Ridley Scott (Gladiator), you are sure to get an epic movie.
The movie is rather long, at just under three hours, but if you don't mind a deep character development process for both Washington and Crowe, then you will thoroughly enjoy this movie. I know I did. The climax was inevitably good (did you really expect Washington's character to not be prosecuted?) and the real-life facts that followed were quite interesting.
For putting two great actors on screen, an impeccable character development, good plot progression, and great real-life story, American Gangster should be on everyone's watch list.