Here's my top ten, there are far too many that I enjoy to make a proper ranking, but this gives an idea of what I like to listen to.
1. Tchaikovsky - I just love all of his work, I really enjoy his ballets, symphonies, piano concertos and many of his other works as well.
2. Vivaldi - I enjoy the intensity of some of his works.
3. Beethoven - His symphonies are definitely on par with Tchaikovsky's if not even better, but I prefer Tchaikovsky's style, although only slightly.
I also enjoy John Williams and Hans Zimmer, although I prefer older composer's works, mostly that from the romantic and baroque era.