Howard Shore (eg. Lord of the Rings score)
John Williams (eg. Star Wars score)
Hans Zimmer (eg. The Last Samurai score)
Nobuo Uematsu (eg. Final Fantasy score)
Add in whoever you think deserves a mention :) Personally I think the most impressive in the past few years has been
Howard Shore for Lord of the Rings while the most diverse composer is probably Nobuo Uematsu for doing notably all those
Final Fantasy scores, and other games of course (don't know what they are).
John Williams has done so many that I can't be bothered to name them all, I'm sure Star Wars probably rings a
bell with his name for most people. Williams' music is probably the most "classic" out of all of them
because of how themes such as Star Wars have entrenched into our minds :)
Hans Zimmer in The Last Samurai was quite good too :) It definitely fit the Japanese atmosphere very well ^^
So who is your favourite? Feel free to mention others. I always like listening to soundtracks.