1. Steven Spielberg
Unfortunately a lot of you probably stopped taking this list seriously right about now but don't worry, by examining the criteria for greatness that was outlined in the introduction you might realize that Steven Spielberg is probably the most under-appreciated director in all of American cinema in terms of historical importance. To be fair to the other filmmakers though, an equally persuasive case could be made for John Ford, Stanley Kubrick, Orson Welles, and maybe even Scorsese of Griffith in this spot. As it stands though, Spielberg is the most iconic filmmaker of this generation and the greatest director in Hollywood history from an objective standpoint, even if you don't particularly care for his films. The first criteria is how their style and films have impacted future films and all you need to do to decide who the most influential director on modern movies is look at the kind of movies Hollywood is turning out no. Of all the other great directors including Welles, Kubrick, Scorsese, and Ford the director modern filmmakers copy most is of course, Steven Spielberg. With Jaws, Close Encounters of the Third Kind, E.T, and Raiders of the Lost Ark, Spielberg created the modern Hollywood blockbuster, which unfortunately has led to many less talented directors trying to emulate Spielberg and failing badly as well as studio heads trying to replicate his box office success by using the same basic formula of his films but not replicating his skill, heart, or vision. Secondly is the regard in which he is held by his contemporaries and by critics, which has been for the most part unanimously positive. Although a small but vocal minority consider his films overly sentimental or accuse his serious films of cashing in on real life tragedy, filmmakers such as Hitchcock, Bergman, Scorsese, Kubrick, Herzog, and many, many others have expressed their admiration for him while most critics consider him a completely natural filmmaker responsible for many modern classics. Hitchcock in particular declared him the first filmmaker to think outside of the visual constraints of the theater, making him one of the first purely cinematic directors to work in Hollywood. The next criterion is how well their films have held up and the overall respect their individual films are held in and Spielberg has one of the most impressive filmographies of any director. His "classic" films include Jaws, Close Encounters of the Third Kind, E.T, Raiders of the Lost Ark, Empire of the Sun, Schindler's List, Jurassic Park, Saving Private Ryan, Minority Report, and Catch Me If You Can while his near classics include movies like Indiana Jones and the Last Crusade, The Color Purple, Lincoln, and even his less well received movies such as War of the Worlds still have pretty significant merit. In short, no American movie director has had a better combination of influence on cinematic form, respect of their peers and of critics, and a more loaded filmography. Although you could certainly make a very good case for Ford, Kubrick, or Welles to be in this place, Spielberg is probably what the average person thinks of when they think of an "American" filmmaker and is the easiest choice for the objectively Greatest American filmmaker of all-time.