You need Ravenloft on that list. And a few others, too (Mystara, for example).
I voted for Eberron, because I am all psyched over the new book; it rocks, but also because of all these settings (aside from Ravenloft) it's the only one on my collect-and-play list, and I have a vibe about it which I haven't felt since my Planscape/Spelljammer days.
My top five list:
1. Eberron
2. Ravenloft
3. Planescape
4. Spelljammer
5. Diamond Throne (AU)