Hmm difficult question.
I dislike the fire dungeons in almost every Zelda game, they're not settings i enjoy but Death Mountain has a place in my heart more for what it does rather than what it is.
I think my favourite Death Mountain would be TP's, i like that Kakariko village is built into the foot of it rather than being a village at the bottom that feels as if it could be placed anywhere else like it was in OoT. Scaling it is a lot more interesting too where OoT's is basically a straight line to the top.
Second favourite is OoT Death Mountain, not because i prefer its design (not saying its bad) but it has a special place in my heart because of the cloud above it. I remember it being said that the cloud above it changes when there is discord, knowing that and stepping out of the Temple of Time after the seven year jump to see the cloud blazing above the mountain, it just felt epic.
I know its not Death Mountain but Dragon Roost is the best fire location and dungeon Zelda has had. <3