C&C Red Alert theme song "hell march"

TES III: Morrowind. As soon as you start that game, then Nerevar Rising is played, which is one of the best theme songs around. Also the road most travelled and some others are great, which are played during playing.
Sacred 2 Fallen Angel. The themesong Sacred is made by Blind Guardian, as well as the combat music. And it fits nicely. It's also a great themesong. Also the random environment music is good and changes when you visit every region. Sound in tyr lysia is different then in artamark or dyr lain.
Myst III: Exile. The music in here fits with the atmosphere around.

Assassin's Creed III : http://www.youtube.com/watch?v=3QByfthwPYU . End of the story.