I feel games needs to follow the movie industry in this and add more developer commentary.
The new version of Deus Ex for the Wii U will have the developers discuss the whole game while you play it, wich is absolutely awesome in my book. Thats almost enough for me to re-buy it.
God of War games has their behind the scenes videos detailing the process, and Valve has brilliant commentary nodes in their games. This seems like a easy and cool way to add some value, i would glady spend an hour or 2 listening to how people approached some sections and themes of their games.