A quick search on the Internet Movie Database reveals that Johann Sebastian Bach's music has been used in at least 873 films. Not bad for a composer born centuries before the first movie was made!
Bach's special mix of the logical and the spiritual makes his music very effective for some films. David Garland presents film scores where Bach's music is used, such as "The Hunger" and "Dangerous Liaisons," where it's adapted, such as "Fantasia" and "The Beast With Five Fingers," and where it's emulated, including "Who's Afraid Of Virginia Woolf" and "The Paper Chase."
Below: Bach's Toccata and Fugue in C minor as used in "Fantasia":