Hmm, several good choices have already been made. Let me just chip in with a few...
"Return" from Radiant Silvergun. Always loved the triumphant march theme it has going on, with the main characters trying to make a quick run to Earth to get some more supplies to survive on, without being noticed ideally. Perfectly juxtaposed with just how much
worse things get pretty much from the onset, which is similarly reflected in the music getting much moodier from then on - outside of maybe
"Evasion".
"Flight" from Panzer Dragoon. I'm pretty sure Sega wanted to outright
wow people with the Saturn, so having a full-blown orchestral piece serve as the backing to the surreal sunken city landscape (complete with impressive-in-1994 water effects to seal the deal) was a great choice. Unfortunately, it must've been somewhat prohibitively expensive to use that orchestra, because they only did two other tunes in the game (the title theme and the credits theme), but what
was done still holds up quite well today. Comparatively,
Zwei's (
"Destiny Begins") is a bit too erratic and shrill, although
Saga's (
"A Premonition of War") is a pretty good tune for coming to grips with the dragon's overworld controls, featuring the credits theme for the first time.
"To the Gateway" from Super Mario Galaxy. Okay, I know somebody in here said it was "Good Egg Galaxy", and that's certainly the first
main level, but this is the first level that actually introduces you to the weird mechanics
Galaxy uses, and I'll be perfectly honest - just listening to it gives me an overpowering nostalgic feeling that often makes me teary-eyed. If that's not a good composition, I don't know what is.
"Reincarnated Soul" from Castlevania Bloodlines. For a series well-known for excellent music, this certainly doesn't disappoint, immediately bursting through the door with this energetic piece. Probably a bit more obscure than any of the numbered entries or
Rondo of Blood, admittedly, although it got
an excellent remix in
Rebirth (not sure why they didn't use
"Battle of the Holy", but I like "Reincarnated Soul" a bit more so I'm not complaining - "Battle of the Holy" would've been better off used in Stage 6 instead of
yet another remix of "Vampire Killer", anyway).
"Terraport"/"Bamboo Mill" from Vectorman.
Vectorman has a pretty great soundtrack filled with fairly subdued techno, and this is arguably the best track in the game (I think I prefer
"Tidal Surge", though). Always good to start with your best foot forward.
There, five more selections. Although the clear winner here is
"Go Straight", of course.