I know i will come off as the shallow guy whose never seen a film made pre Star Wars, doesn't know who Scorcese is etc, but really can anyone compete with John Williams. The Whole Liet Motif thing (giving characters themes that change as the mood changes) and the fantastic main themes. Endlessly versatile he has simply created the best movie soundtracks ever. Listen in awe as Williams does:
Wonder and awe - Jurassic Park
Adventure and Derring Do - Indy Jones
Scary - Jaws
Sentimental - ET
Wierd - Close Encounters
Majesty and Power - Superman
Sadness and Mourning -Saving Private Ryan
Military Might - Imperial March
The Star Wars theme - Star Wars

I also love the soundtracks to Blues Brothers, Back to the Future, Sergio Leone Westerns, North By NorthWest, Halloween, The Omen, Psycho, Blade Runner and Batman.
Feel free to criticise.