This list is so cool! It's awesome to see that I've seen a great number of these films- esp the John Wayne ones 
Very thorough list! Everything from the Marxs Brothers, Shoot-em-up classic westerns, gangster/mafia movies, Hitchcock thrillers, sci-fi, family movies, historical fiction; Horror, comedy, murder and romance. Also intrigued that Gone with the Wind is fairly far down on the list.
I applaud who ever took the time to make this list. Yay for the Brits for saying which American movies were the best!
