Bob Shingleton's commenter, named simply "kea," suggests that it requires knowledge and attention to listen to the music of Bach, Haydn, and Mozart (and a random list of composers including John Cage). Shingleton agrees, but I think that film music is vastly different from music that we listen to without a "vision track" and a screenplay. Here's my comment:
Film music is structured differently from the forms that Bach used (dance forms, fugues, binary forms). Bach's music was the "event" itself, and not the underscoring of the "event." Film music is certainly structured differently from the forms that were used in the Classical Period (Sonata form and Rondo form in particular). Again, the music was the "main event," and not its underscoring. People who listen to music of the Classical Period and the "main event" music of the 19th Century appreciate the organizing forms, even if they don't know how to identify them. These forms are great for organizing and developing material in meaningful ways, and they are still in use. It's kind of like the five-act or three-act form used in plays. It's kind of like the modified three-act form used in films and in television. It's kind of like the standard expository form that we expect when we read a short story or an essay.
Film music uses techniques learned from Wagner by way of Schoenberg, Herrmann, and a bunch of other genius composers, like Friedhofer and Copland who flourished during the second half of the 20th century. They exploited motives, introduced instability by using techniques like ostinato and atonality, and brought in unusual instruments for the time like the viola d'amore, the alto flute, and the theremin. Their main concern was to expand the moment, and not to have the music as the "main event." Of course the greatest underscoring melds with the action, and eventually suggests the action or the story itself. Sometimes themes from a movie will form the title music and will function like an overture. That is the technique of Rhapsody or stitching material together.
I have the greatest respect for film composers and for film music, but functional film music is not interchangeable with "main event" music written using classical forms (or post-classical forms).
There is great music written as underscoring for television. Listen sometime to the various themes written for Lassie (and probably orchestrated by a handful of other composers trying to make a living doing "piece work"). They are fantastic. Listen to the music Nelson Riddle wrote for Route 66 and the Naked City. Mission Impossible also had great music, as did the Twilight Zone.
21st Century film music can be extremely good. John Williams continues to do extraordinary work, though sometimes it can become distracting, as in the case of the Lincoln movie. When the music is too good (or too much in the foreground), I find it difficult to pay attention to what the actors are saying.