The bulk of Gradius's most crowning songs accurately convey some sort of cosmic wonder. Talk about what you consider Crowning Music in Gradius here.
"Tears Began Gushing", the bonus stage music from Gradius 2 on MSX. It always sounds like you flew to heaven or something, especially considering that most of the time, the entrances to these bonus rounds are welcome escapes from some very difficult levels.
"Battleship" from Gradius V. It starts with the first few notes of the first stage theme from Gradius I, then kicks off into a high speed techno beat as you blast away enemy ships. The awesomeness level is taken Up to Eleven when it is Mickey Moused into the opening.
Maximum Speed (Fate...) from Gradius Gaiden. It starts out awesome, then gets more awesome as it picks up speed.
Gradius. One of the best soundtracks to any arcade game.The NES port music isn't as great but it's still brilliant.
From Gradius V: Impregnable Fortress, the rave-like music to the second part of Stage 7.
Maximum Speed from Gradius II. It plays in the high speed level, and it's very fitting for a level that goes very fast.
Sensation, from Salamander 2 Stage 2, also featured in Keyboardmania 3rd Mix.
Also from Salamander 2, Fire Tripper, which to the dismay of this troper isn't used in the game. Fun fact: The Salamander 2 soundtracks are partially composed by Naoki Maeda, who would go on to become a major producer of Dance Dance Revolution songs.
Speaking of DDR, Burning Heat! (Full Option Mix) is a remix of Gradius II Stage 1's music first appearing in Beatmania IIDX 7th Style and DDR 7th Mix (as a shorter, "3 Option Mix" version).
Silvery Wings Again also deserves a mention, also includes a shout out to "Departure From Space" from Gradius III
High Speed Dimension from the SNES version of Gradius III. Just like the stage, it starts out deceptively slow, then it Immediately kicks it to high gear, just like the stage.
What? We got this far without mentioning the immortal Aircraft Carrier aka Boss Rush theme? Especially its mix from V.
