Blarg: Loved Heretic. Very brightly colored, fun maps with great decor. It was a monster hunting and dark devilish doings ... with a smile. I was terrifically disappointed in the grim, limited color palettes that came after.
kalirion: Lol, I loved Hexen for it's atmosphere and levels with character, and didn't care too much for Heretic.
Most people said the same thing. The Hexen/Quake visual style took over from the DOOM/Heretic style with great success, at least partly because the games kept getting more visually sophisticated in other ways and the ability to hook up with other players just got better and better.
Me, I stare at the dull insides of offices all day long. Everything is already beige and grey, and already has its own kind of oppressive industrial gloom. Doom and the first Heretic were like opening the door for me; Hexen and Quake were like the teacher telling you to come inside after recess.