People, especially enthusiasts of classical music, sometimes criticize John Williams for being a bit repetitive and over-bombastic. But, well, he's first and foremost a film compose, and that's sort of the nature of the genre. People tend to select film composers because they liked their previous work and want something very similar, so they tend to have a pretty consistent style. You see the same with other prominent film composers like Hans Zimmer. I guess what's notable about John Williams is that he was such a prolific and popular film composer for such a long period that his style was the style of film scores for a generation. It's hard to imagine an era of film, hits like Star Wars and Indiana Jones and Jurassic Park, without his bombast. His tendency to "go big" is part of what defined these epics.

All that said, my favorite John Williams composition strays a little bit from film. It's "The Mission," better known as the theme for the NBC nightly news. The short theme is instantly recognizable to probably most Americans, but not so many have heard the full composition. NBC used to play it over credits at the end of the last news segment but I don't think they do any more. Fortunately there's a (potato quality) YouTube video of John Williams himself directing a Sony studio orchestra: https://www.youtube.com/watch?v=l7kIgcYgIQk