Some of my favourites:
- Ninja Gaiden - 4-2
- Arkanoid C64 Version
- Castlevania - Stage 3
- 1943 - Mission Theme
- Turrican - The Deep C64 Version
- Double Dragon - Title Theme
- Double Dragon 2
- Mercs - Mission 1 Arcade Version
- Metroid - Kraid's Lair
The greatest main theme of any game:
DOOM 2016
The whole thing, really, but in particular...
Track 11, BFG Division is the most popular.
2, Rip & Tear.
4, Rust Dust & Guts.
8, Flesh & Metal