Ultima Underworld: The Stygian Abyss - Closest modern equivalent?

This was my first ever experience of a dungeon crawler and I was completely hooked and somehow managed to finish it.

I've always wondered what the closest modern successor to it might be. I just loved the first person feeling of solitude down there and the layers of dungeon getting more and more dangerous as you explored them. I also loved that there were factions that could be friendly in there and that you could trade with. Does anyone know what the nearest equivalent to this masterpiece might be?