Hitchcock once said, "I'm a typed director. If I made 'Cinderella,' the audience would immediately be looking for a body in the coach." In other words, Hitchcock stuck primarily to one genre, although it's worth recognizing that "genre" can be a limiting concept if relied on too heavily. There were always distinctions in Hitchcock's work. Most of his films could best be described as "thrillers" or "suspense" films that came in the form of espionage, slashers, romance, film noir, horror, and other variations. Yet he did not merely make thrillers. Hitchcock is commonly credited with inventing them and several of their subgenres, like modern horror, hence his nickname "Master of Suspense."
Spielberg is impressive and influential in a different sense. Like Stanley Kubrick, he's conquered several genres, finding ways to attribute his mastery to completely new film expressions. He's made sci-fi films ("Minority Report"), historical dramas ("Schindler's List"), horror-thrillers ("Jaws"), slightly romantic comedies ("The Terminal"), adventure films (Indiana Jones), kids films ("E.T. the Extra-Terrestrial"), war films ("Saving Private Ryan"), and more.