This discussion has forced me to ponder my own preferences and prejudices in the genre. This is strictly a personal list. Feel free to ignore it.
- Terminal based
- ASCII interface available if not default
- Turn based play
- Still under active development (perhaps open source)
- Complexity (you encounter something new every game, forever)
- Difficult but not impossible for mere mortals (can include permadeath)
YMMV
My xnh elven ranger is contemplating the lower mines...