About deep, mature stories: bring them on! I love games that touch mature themes, and I think adventures are ideally suited. Anyway, I wanted to comment on our weird cousins, the I.F. guys. In my (brief) experience with these games, I was amazed at the literary level of these works. Some of them are just crying to get some graphics, some voice acting, and voila, masterpiece.
See:
http://www.ifarchive.org/
