But Duke Nukem Forever is
"Still in development"! They haven't given up yet!
As for me, I just don't come up with ideas for what's going to be in a game when I start. I look at what is available and I think, "Hmm... what happens if I do this?" And I try it. And then either its really cool, it doesn't work, or it's just stupid. In the first case, I leave it in and go with it, develop its idea, see if I can make it even better. I'm just not the kind of person who can come up with really great ideas out of nowhere that can be easily translated into a game. I mean, sure, I could probably plan out a game, but that plan would usually be difficult or impossible to implement. If I'm designing as I go, the design is based around the already-present capabilities of the system I'm using.
One big GDD comes to mind that was a huge, great undertaking. It sounds like a cool game by today's standards, but it was written in 1993. The final product was almost unrecognizable from the GDD. They had level designs, items, storyline, characters, enemies, definitions of specific graphics and sounds needed, and all that stuff, which was mostly removed from the final product. If I read it, I would have gotten about half-way through the document (and it's long) before having realized what game it was talking about (if not for the title on the front). The game?
Doom
