Music within Video-games set the tone and atmosphere. Be it a temple in Skyrim or the bridge of the Normandy, music is well and truly needed. However, not every game has amazing soundtracks. Some games lack the this last piece of the puzzle.
The one thing that is needed to sell a game to me is its opening track. If the developers fail at this then the game doesn't look very good to me. If the opening track gets me pumped and ready to play the game, then the rest of the soundtrack has to be good. This is were some games fail. This could be annoying battle songs or dull, pointless cut scene music which makes no sense.
So what are you most Favourite or most Hated soundtracks of all time? My favourite soundtrack is Final Fantasy 6 and my most hated is Avatar - Legend of Aang for DS.