I voted Greyhawk, but I'm not sure I actually would. I kind of like that it's not over-defined. OTOH, I do like what Erik Mona's done/is doing in the LGJ, Polyhedron, Dragon, and now Dungeon; so maybe I would buy it. And if there was a really cool, interesting expansion of the setting (like, what's on the rest of the world?), I might buy it.
OTOH, I might think it was lame, and not buy it.
So, really, my vote should be "Any, if they were done well."