The contribution of Alfred Hitchcock to the suspense thriller genre has been in essence to define it so that all subsequent films in the genre will aspire to the standards he set and will be compared to the films he made. This has indeed been the effect, so that films that have nothing to do with Hitchcock's style, themes, or interests are said to be Hitchcockian thrillers by those seeking a superlative. An example playing at the present time is The Crying Game, a film compared to Hitchcock though it is not a Hitchcock-style film at all and only touches on Hitchcockian themes in terms of generic elements that are difficult not to have in a thriller.
Hitchcock's contribution has been much broader than merely to the thriller genre, however, for he influenced a generation or more of filmmakers who learned from his films how to manipulate material, manipulate the audience, and satisfy that audience at the same time. He was meticulous in developing his films, storyboarding every shot and showing an understanding of both camera movement (in the Murnau tradition) and montage (in the Pudovkin-Eisenstein tradition) that makes his films useful as "textbooks" of technique. He started in the silent era and never forgot the power of the image, but he also adapted to the use of sound in a way that showed he regarded it as an essential element in film thereafter (witness his experimentations with sound as in the scream that turns into a train whistle in Murder or the musical experiments he made with the use of "The Merry Widow Waltz" in Shadow of a Doubt). He experimented with color once the film medium required more color - he stopped using the backlight for hair highlights in Vertigo, reasoning that color was sufficient differentiation; he used color for its psychological power to illuminate character (as Robin Wood discusses with reference to Marnie [1965: 153-184]); he used 3-D as a way of creating a new sense of space in Dial M for Mur...