Sound designers can provide incredibly detailed sound, so real it's like your in the characters shoes in the game. Not only the characters and background music come into play but also other everyday sounds like footsteps, wind and even echoes all make the experience that little more realistic. Doing something like closing your eyes and listening to the sounds in the game creates visions of what is happening in the game.
When the budget has to cut back, the audio is the first to go. The audio in games scale down a bit because of their large files. This is also due to their high quality. And just like all areas of the gaming industry, you need a music license.
For me i find it hard to pay attention to most music in games. They are some memorable ones, one of which is in Final fantasy VII at the end of a battle and also the 'Steel samurai' theme in Phoenix Wright. I will listen to the music when i am progressing through the game but when leveling up i do listen to my own music on iTunes. This is because the game music will annoy me to hell.
One of the best places to find in game music is at BeeMp3, Bearshare/limewire and there was Galbadia hotel but its unavailable. Also my friend gave me all sorts of websites but they are somewhere in my bedroom back at Middlesbrough.