Cool thread.
Question: How many adult games have you PAID for?
This will answer the question if it's a viable project.
So many games gets cracked and exchanged on P2P...
I could do a 'not too crappy' adult game if anyone is willing to fund the development. I've done 3D games before. I stopped when I almost got bankrupt on my third game... Now I'm only working on it part time.
A really cool game would be with stereo goggles and a glove (on the hand you won't be using

).