Of all time? Not sure but as far as games go Skyrim has one of the best I have ever heard. All of the music in that game is perfect for it and really gets you in the right mood.
Skyrim and Oblivion have some of the best, The song of Sovngarde was just perfect. I also loved the fell it gave you while killing a dragon (DIE DRAGON) however i also love Skyward sword's soundtrack as well. Guile theme is obviously the best because it goes with everything.
The original Fable scores, by Russel Shaw. It's just so magical and fairy-like while still being dark and mysterious.
Im not exactly sure about all time, but if I had to pick I'd go with Skyrim and maybe even Napoleon total war. Both have some great soundtracks. Maybe even Fable II.
The LotR soundtrack is absolutely amazing, I really need to get it on my mp3 player some time. Other favourites include StarCraft 2, Fallout: New Vegas, Paradox Grand Strategy Games, the Pokemon games.
Movie wise, I'd just say the Coen brothers (or more accurately, Carter Burwell) in general. No Country for Old Men, True Grit, Blood Simple. Blood Simple Game wise, it's hard to choose between Red Dead, Frozen Synapse, Majora's Mask/Ocarina of Time, and Chrono Trigger. Red Dead's music is so perfect because it isn't just a soundtrack, but can tell you what's happening in the game, and it's very thematic and epic. Frozen Synapse is very atmospheric and suited to the kind of game it is, a more exciting version of chess. Majora's Mask/Ocarina of Time because they had just bizarre, almost avant-garde songs that amplified whatever mood was trying to be set. And last but not least, Chrono Trigger, simply because the soundtrack was just really good. Red Dead Redemption (I remember this song completely taking me by surprise for reasons obvious to anyone who's played the game) Frozen Synapse Majora's Mask Ocarina of Time Chrono Trigger
For a gme I think MGS1 had an amazing soundtrack Also MW2 had a fantastic soundtrack for a craptastic game. But why? Becouse it had the mofo Hans Zimmer as the composer. For movies I'd say The Nightmare Before Christmas had an awesome soundtrack.