Originally posted by SiEgE:

Audio tracks actually don't take much space, unless the game is very dialog heavy, with variations and etc. Textures is what takes the biggest chunk of the game's size.

It really depends. Support for additional languages also contributes a lot if there's lots of spoken audio. I think FF13 had about 40 GB of videos and audio and you could slash that in half by deleting the japanese or english versions. The rest of the game was like 8-10 GB lol.