Ack, so many of the songs I were going to list have already been taken! And yet, I also see many songs listed, that while may be good, are no means powerfully epic. C'mon people, it's not a "post your awesomest song!" thread, it's for epic, grandiose, blow-ye-away-with-emotion music!

And on that note, here are my additions:

Star Ocean Blue Sphere - 1-10 - Legacy from the Past
Star Ocean Blue Sphere - 1-12 - STAR OCEAN FOREVER
Star Ocean The 2nd Story Fantasy Megamix - 04 - Silent Universe
most of the Onimusha 2 Orchestra Album
Medal of Honor Frontline - 11 - Arnhem

One that I recall being an outstanding soundtrack was from the Dreamcast game "Sword of the Berserk" by Susumu Hirasawa. That had some unbelievable work in it for the sentimental moments in the game, especially the end credits and "Rita's Grief" which was also a beautiful rendition.

I'll have to second Communication Breakdown from Xenosaga Episode II and Awakening from Xenogears, two tracks that I really find epic.

As for the rest, lemme think...

Blaze Heatnix Stage from Rockman X6

Xenosaga II Main Theme

On the Banks of a Dream: Anothe World from Chrono Cross

Frog's Theme from Chrono Trigger

Hikari -Kingdom Orchestra Version- from Kingdom Hearts

Unfinished Battle With God Syndrome from Valkyrie Profile

promised pain from Xenosaga Episode III

just to name a few, there are many others I can't think of just now...

I know it's from a movie, but "Navras" is the most epic piece ever created. "The Chase" from National Treasure, too.

For games, hmm.

-One Winged Angel (Advent Children: Teh Pwns)
-The Last Confrontation (KOTOR)
-Memory of the Wind (Final Fantasy III on DS)

I'm going to check out this Ace Combat stuff...

My first post /\

Edit: Somebody else put down Feena. I didn't say it because it seemed not epic enough, but I guess it is very moving.

I can't believe nobody's touched on this yet:

Xenosaga Episode I: The Escape

Starts with dread, then becomes a sweeping, epic fanfare of evil. Would have been a great last boss battle, but... well, anyone who's played the game knows what they did there.

The ones I like.

Soul Calibur II - Confrontation, Sword of the Patriot and Hubris.
Viewtiful Joe 2 - memoirs of an Invincible Monster
Metroid Prime - Underwater Rector Core
Prime 2 - Hunters
Baten Kaitos - The True Mirror
Chrono Cross - Time's Scar.
Gradius V - Intermezzo
Tales of Symphonia- Fatalize
Secret of Mana- Phantom and a rose, Danger
Megaman x5 - Volt Kraken Stage
X6- Infinity Mijinion (sp?)

...

Chaos Legion OST - Massive Strokes as well as the whole dang OST.
Spartan: Total Warrior - Talos
Castlevania: Resurrection - Have Mercy
Unreal Tournament - Skyward Fire, Botpack #9, Serenity (2004), Level 8 (2004)
Prince of Persia: Warrior Within - Main Theme
Battlefield 2: Modern Combat - Main Menu Theme, couple of in-game themes.

I'm very surprised with the lack of mentions for Shadow Hearts and SNK's awesome sound team. Those two teams have created some of the most powerful and moving songs I've ever heard in video games, including many of the mainstays already mentioned in the thread.

I love Revived Power - Battle with the Colossus from the Shadow of the Colossus score. I've never played the game and I know I never will, but this track is thrilling. When I think of the term 'epic' this is the music I imagine:

http://www.sendspace.com/file/ct5e1q

Sorry for zombieing this thread, but I agree with Kanzaki with his SC2 choices, except I'd replace Confrontation with Healing Winds (original and remix). Unlike (what I assume to be) most others, I also like the US version of Hubris over the Japanese version, since it sounds like it uses an actually chinese instrument, the erhu, for the strings, making it sound more traditional/authentic. The original version seems to either use western string instruments or is electronically rendered, almost kind of dumbing it down.

I already nominated this song for Song of the Year so it's only fitting that it gets a mention here as well: Keiki Kobayashi - Naval Blockade [Ace Combat 5: The Unsung War]. That song is 3 rock-solid minutes of pure, unadulterated EPIC.

Street Fighter Alpha 3 - Zangief's Theme and Hi-Tech. Great songs with epic melodies that convey the personalities of their characters to the highest degree.

These probably have been posted before, but whatever:

FFVI - The Dream Oath
FFVII - One-Winged Angel
FFVIII - Liberi Fatali
FFXI - Opening Theme

Those are the four most "epic" FF songs, in my opinion. That said, my favorite of all time is Eternity from FFX-2 (particularly the piano arrangement).

Final Fantasy VII Main Theme - A lot of nostalgia comes along with this one, and it complimented the game so well.
Life, A Distant Promise (Chrono Cross) - Purely epic. I can't really even find words to describe it, it moved me that much.
Small Two of Pieces (Xenogears) - My all time favorite. I heard it on this particular site about six years ago, and DAMN. I was blown away even then, without the context of the game itself. Beating the game a few years later made it even better, and I'm still amazed every time I listen to it. Joanne's voice really complimented the music (moreso than the Mebius singer, methinks) and the guitar solo still brings a tear to my eye.

Healing Winds - Soul Calibur II & III
Going to Where the Wind Blows - Soul Calibur II (think)
Unforgotten - Halo 2
Glorious Victory - Dead or Alive 2

...these would have to be my favourite ones :D

To me, "Betrayal" from the Silent Hill 2 soundtrack is epic, since it's so filled with emotion. Whenever I listen to it I get a feeling of total hopelessness.

Vagrant Story - 22 - Great Cathedral Attic/Large Chapel Garret

This song seamlessly intertwines despair and hope at the same time. It's not long nor complex, but it really brings you down with emotion. Especially in the context of the scene it was meant for. VS is regarded as (one of) Sakimoto's best works, and I highly recommend you listen to it if you havent already. 03 - Climax of the Greylands Incident is also one massive 11-minute epic orgasm, and so is 29 - Staff Roll.

I'm a bit surprised that there haven't been any Medal of Honor tracks posted yet, so I'll add a few.

Medal of Honor: European Assault - Dogs of War
Medal of Honor: European Assault - To Stalingrad
Medal of Honor: Airborne - Main title
Medal of Honor: Airborne - End Credits

I tend to find the MoH "epic" songs to be almost a breed of their own. They do an excellent job evoking images of the valour, courage and tradegy one only finds in war.

If you're interested in almost "over-the-top" epic, I recommend "Hero's Theme" from Kameo Elements of Power

A lot of the WoW/Burning Crusade tracks have a very epic choral feel to them. In particular, I love the theme for Stormwind. Ironforge, Thunder Bluff, and A Call to Arms are all good tracks from the WoW soundtrack. I haven't listened to much to the Burning Crusade stuff but there's some gold in there as well.