If you ever see the artworks behind each area you will easily understand how hard they tried each area to be it's own unique thing. There's a huge contrast between all of them. Lordran is filled with hollows, but that doesn't mean it has to be a complete ugly mess.

So, you will get "normal, low-class" areas such as the Undead Burg, "filthy" areas such as Blighttown, "high-class, glorious" areas such as Anor Londo and so on.

The other souls games also have their own strong art styles, but they ultimately sacrifice some of that subconscious effort of giving each area it's unique identity. And that's not necessarily a bad thing, but it is indeed something that Dark Souls does different.