I get it but Im not only one who posted random themes besides main theme … also there are main themes in my post too … sometimes main theme is not that good like character or battle themes 
So a few pages back, someone here linked a couple videos to Zelda: Ocarina of Time soundtracks… Holy shit the fuckin’ nostalgia gave me a hemorrhoid of memories up the ass- It hurt so good. Thank you, sir, for stimulating me in such intense ways.
And, to contribute: GOD of WAR Soundtrack: The Vengeful Spartan [main theme]
The orchestra really nails that greekmythology/badass/intense feel.
Battlefield. Definitely Battlefield.
The only problem i have with the Secret of Evermore soundtrack is that they couldn’t possibly cram enough awesomeness into a single SNES cart. The open to this album gives me goosebumps every time at 1 : 30. i haven’t had time to play SoE, but i listen to the soundtrack regularly, both orchestrated and chiptune.
Pretty much anything out of Jeremy Soule goes on my list, including Elder Scroll’s themes.
-Kawai Tei-
EDiT : Though it’s probably not the opening theme, BF2’s menu music (the first thing you hear) always makes me tense. This has been literally the going themesong for every LAN party i attended from '05 to '09. Not because it’s a good song, but because there was always at least one putz who came to the party unprepared (usually me) who’d hold up the game. Everybody’d be waiting to play while surfing network share folders and swapping warez with this looping over the scoreboard server’s speakers. sigh i miss those days.
I feared that I wont see this 
yeah Heroes of m&m III^^
also Red Alerd I&II theme songs are awsome
Doom E1M1 (I think this is theme song yes?) and it just cant be missed E1M8 is also the kickass song.
and Mafia as well.
Doom and Duke Nukem are sure winners for me.
Seriously, guys? I am disappoint. :hmph:
https://blackmesasource.com/media/music/BMS-01-theme.mp3
and look, it’s a THEME song! :awesome:
Not being a suck-up, just wanted to make that clear. I’m madly in love with a lot of the songs mentioned earlier, like AC2, Morrowind, Diablo, etc. But the BM theme needs to be mentioned too.
Oh holy power here! I totally forgot about that!
Don’t know if that technically counts as a theme song, since they just used Song 2 by Blur.
https://www.youtube.com/watch?v=qn8kNA85RFY
mmmmHH HU HU HAHAHAHAHA AAAAAAAAAAAAAHHHHAHAHAH
https://www.youtube.com/watch?v=Mv5Jvr2Fp48&playnext=1&list=PLC65C2329E2BE9EB3
https://www.youtube.com/watch?v=78cCEPL_MLY
https://www.youtube.com/watch?v=MVpn4qLzmiY&feature=related
https://www.youtube.com/watch?v=x_jUcfZR3Xc
Cigar in you mouth is a requirement for these:
https://www.youtube.com/watch?v=SbevUYP55HI&feature=related
https://www.youtube.com/watch?v=Rz7Sexypf3I
not a “main theme song” but I don’t think a good immersive video game has a “theme song” anyways. it has tunes that set/compliment the atmosphere/mood/etc.
and no game that I can recall did that better than SS2
in normal everyday noise I’ll still hear what sounds like a couple of notes from the ops deck or the garden, and instantly be transported back to the Von Braun, ahh good times
ops 2 track probably my fav
https://www.youtube.com/watch?v=Z5yVOFokLVY
https://www.youtube.com/watch?v=lkkD3TLaOfA
Kingdom hearts! Made me play the games again because of the song
https://www.youtube.com/watch?v=jWtX0C34hfE
I know it’s not a main theme but the music which plays while installing the game. Oh god, brings so many memories