I have equal fondness for Heretic and Hexen. I kind of just looked at Hexen as "Heretic 2"....then they made a Heretic 2....and a Hexen 2. So I clearly was wrong.
Folks would do well to check out the glorious/bewildering Serpent: Resurrection---slim pickings out there in terms of fan reckonings compared to Doom and Quake by far, but it has heart and has been seeing updates for some years strong now.