Doug McCrae
Legend
I don't think any edition of D&D does horror well. The system requires lots and lots of fights to balance fighters against wizards, and you simply can't have that in horrror.Ravenloft is probably better outside of 3.5/4e.
Even Clark Ashton Smith-style 'greedy treasure hunters getting their comeuppance' requires far fewer monsters than traditional D&D, and a slower pace. Lurking menace, not 5 goblins in a room.
Does D&D do anything well apart from D&D? I'm not sure that it does.
Ravenloft would probably best suit a system like GURPS, BRP or (I guess) Chill. Possibly Unisystem, but I wasn't too impressed when I played a session of All Flesh Must Be Eaten. Level-based systems are great for "I'm Gandalf, You're Conan, We Fight Dracula", but are terrible for actually being _afraid_ of Dracula.