I don't know how this guy is missing a forum of his own...
For me (and I suspect many others), the Leopold Stowkowski arrangement of The Rite of Spring for Walt Disney's Fantasia (accompanied by animated dinosaurs— What more could a kid want?!?) marked my introduction to Modern era classical music.
For some time, Stravinsky was my favorite composer, and I still hold him in particularly high regard. I daresay that it was Rite of Spring that shook the very foundations of the musical world and pretty much brought about an end to the Romantic era. Certainly, Romantic music continued to be produced, but the political climate of the world and Europe in particular called out for a musical language that was capable of expressing raw turmoil. In emphasizing unusual rhythms (and furthering the unusual harmonies being explored by folk-inspired nationalist composers), Stravinky delivered that idiom, and the musical world hasn't been the same since. Nor did he stop at primitivism— he was a leader, not a follower, at the forefront of later trends in neoclassicism and serialism.
To this day, and probably for the rest of my life, he will remain on my list of the top composers of all time, in the company of Beethoven, Wagner, and Mozart.