Planes, Trains, and Automobiles.
Planes, Trains, and Automobiles also works because it has the advantage of being in the hands of John Hughes, who not only makes this a great movie because of his talent as a filmmaker, but also because he makes use of casting. For instance, the before mentioned car rental scene. The rental agent agent has a very small role. Other than just sitting there and taking Steve Martin's rant calmly, she does very little with her under three minute screen time. But now I ask you, can you picture anyone else doing that scene? It was pure perfection. That part was played by Edie McClurg, and she had previously worked with Hughes in Ferris Beuler's Day Off, playing the principle's assistant. That was a much more expanded role, but clearly Hughes knew her well enough to know how to best utilize her talents.
Planes, Trains, and Automobiles works as a great film because it has all the elements to work as such. It has a perfect of blend of comedy, drama, and heart, coupled with the setting of Thanksgiving, a season synonymous with both hectic running to get things done, and spending time with one's family. It truly is an amazing film that embodies all of these elements. It is difficult to create the kind of chemistry that Candy and Martin share on screen. It is even more difficult to make a movie as entertaining as this one was with basically only two characters. Granted, it is not like a Robinson Crusoe story with zero supporting cast, but in general, what makes this movie work are the scenes with only the two main characters, and after watching it, I feel that these two actors under the directing hand of John Hughes could have easily made a two character story.Although in their own way, I think they already have.