I voted for music. Maybe because I am a musician myself. But I think, that great music could stimulate you to continue investigating the "goddamn", at first look, game and further playing it. I can remember Betrayal at Krondor, which MIDI I wanted to download for separate listening, Hexen and recently bought game Kult: Heretic Kingdoms. I think, the list is far not complete.
But, in all, all things, listed above, must be on as higher state, as possible. In ideal...
