Not only did Williams compose the music for some of the most iconic blockbusters of movie history -- in addition to Superman, Raiders of the Lost Ark and Star Wars as mentioned above he scored several Harry Potter movies, Jaws, Close Encounters of the Third Kind and E.T. -- he also wrote for some of the most important movies of the late 20th and early 21st centuries such as Schindler's List, created the theme music for four separate Olympic games, conducted the Boston Pops Orchestra for 13 years and wrote concertos for clarinet and cello which were performed by world-famous artists of both instruments such as Yo-Yo Ma.
You could make a good argument that Williams' music went a long way in helping the Star Wars movies succeed. Harrison Ford, Alec Guiness and James Earl Jones aside, the original trilogy was not blessed by great actors in its leading roles (I've heard some people say that the acting talent displayed by Anakin Skywalker portrayer Hayden Christiansen is the most convincing proof imaginable that he is the father of Luke Skywalker, played with equal skill by Mark Hamill). Nor did George "Hold me, Ani" Lucas give them the greatest words to say.
But surrounded by and supported by Williams' evocative and brilliant music, they managed to carry us a long time ago to a galaxy far away. Watch the Return of the Jedi scene where Darth Vader finally passes, finally seeing his son "through (his) own eyes." Hamill's blank-faced mooning doesn't sadden us at that death, but the bare piano chords of The Imperial March in the front over the muted sounds of a collapsing Death Star do. Hayden Christiansen's leaden attempts at fury over his mother's death in Revenge of the Sith are more pitiful than enraged, but as that same Imperial March begins to creep forward into the Anakin's Theme Williams composed first for The Phantom Menace we can believe we're watching the Dark Side start to lay its claim on Anakin's soul.
Well, that may be more analysis than a couple of blockbuster popcorn flicks need, so let's just close by wishing the astounding Mr. Williams a happy 80th and prepare to sing "Happy Birthday to You."
Accompanied by a 100-piece orchestra, of course.