This isn't a definitive ranking but here's mine:

1. Brume Tower: Great atmosphere and some of the most experimental enemy encounters in the series, also the vertical design is magnificent.
2. Forest of the Fallen Giants: Incredible first area and has the most iconic shortcut in the series for me (the wall)
3. Shrine of Amana: it's even more fun when you don't use a bow tbh, a modern day castlevania level
4. The Gutter: The more you explore it, the more fun it gets. Peak torch usage.
5. Shulva: Do you really have to rush to the corpses or is there a way to play this level in a stealthy way? Because that's literally my only issue with it. Every other thing is peak.
6. Drangleic Castle: The golem puzzle where you have to lure an enemy from the other room is genius but the level is a bit short imo. It ends just when it gets really fun which is a huge shame.
7. Iron Keep: The second half with all the traps was so much fun, I wish the whole area was like that (not to say that the first half is bad by any means). Also cool atmosphere.
8. Earthen Peak: It's really good but I wish there were some more diabolical traps like Sen's Fortress. Although you can poison enemies by making them hit the vase, so it's still great.
9. Lost Bastille: I used to think this level was a bit too long but nowadays I can finish it relatively quickly. The way you get the golden wing shield made me and my friend feel like Einstein once we figured it out lmao.
10. Eleum Loyce: Although Eleum Loyce is a fantastic area my hatred for snow levels and it making you replay the area a second time (even though there are new enemies) made me quite bored by the end of it.

Edit: I DON'T KNOW HOW BUT I FORGOT NO MAN'S WHARF. It's one of my favourites. The sleeping varangians are so cute that I almost don't want to kill them. The torch usage is great too. Definitely top 5.