Como dito em este artigo da wikipedia :
Donald Leroy LaFontaine (August 26, 1940 – September 1, 2008) was an American voice actor who recorded more than 5,000 film trailers and hundreds of thousands of television advertisements, network promotions, and video game trailers.
He became identified with the phrase "In a world...", used in so many movie trailers that it became a cliché. Widely known in the film industry, his nicknames included "Thunder Throat" and "The Voice of God".
LaFontaine claimed that company National Recording Studios he worked for first came up with many of the famous movie trailer catch phrases, including his own future signature phrase, "in a world...".