Ninja Gaiden/Awesome Music

Ninja Gaiden NES

 * Ryu's Determination (Act 4-2's BGM) from the first NES game.
 * The version used in Ninja Gaiden Shadow for Game Boy, Stage 3.
 * Arranged version of Stage 3.
 * And leave it to Koei to remix Hayabusa's theme into more awesome in Musou Orochi 2 here
 * Reflection (Act 5-3's BGM) from the first NES game.
 * Thunderstorm (Act 2-1's BGM) from the second NES game.
 * Act 4-2's BGM from the third NES game.
 * Chaosium Sword (Intro Theme) from the second NES game, Dark Sword of Chaos.
 * The rather sad tune Tragic Fate (Act 6-4's BGM) in the first NES game.
 * All three games have a great boss theme.
 * The Parasprinter (Act 3-2's BGM) from the second NES game.

Nex gen Ninja Gaiden

 * The three games' Main Themes of course.
 * Alma Awakened has an appropriate enough atmosphere for said boss.
 * Emperor, another of the first game's iconic themes.
 * Pray to God has a melancholic tone and a very appropriate title, considering that you hear it just before fighting Alma…
 * Arachnoid and A Masked Curse are pretty epic for first-level boss themes.