Really hard for me to choose 1.... so
Sonic Boom (Sonic CD)
Sky Sanctuary (Sonic Generations Remix)
Reach For The Stars/ Final Boss Phase 2 (Sonic Colors)
His World/Final Boss Version Phase 2 ( I don't want to speak about it)
Live & Learn (SA2)
City Escape (SA2) / Sonic Generations Classic Version
Metal Harbor (SA2)
Endless Possibility/ Final Boss Version (Sonic Unleashed)
Ice Cap Zone (Sonic 3)
Mystic Cave Zone (Sonic 2)