@JGarret: Wikipedia has a nice summary:
http://en.wikipedia.org/wiki/Duke_Nukem_Forever#Development_history
Basically they were constantly upgrading to the latest and greatest engine, scrapping a lot of created content in the process. They started with the Quake 2 engine, then went to Unreal Engine then Unreal Engine 2, which has been heavily modified by the development team since then. They also changed to another physics engine.
At one point they allegedly scrapped 95% of the level design...
My Mario Kart Wii friend code: 2707-1866-0957







