For me, I want a world that is really different. It's hard to make a setting that is different than the others because so many people will complain that it's too different, but yet if this world has a race, let's say they are called Cymarilians, have light green tinted skin, live in crystalline cities that appear to be made of glass but yet is as strong as steel, and then give them pointed ears...we all know that many people would say that this race is this world's elf race, and that they should live in forests, and because of this difference they would then say that this world wouldn't fit for D&D because it's too non-Tolkenese.
I'm not saying that everybody would say that, but a majority of D&D players would I think, and therefore wouldn't want to play or purchase a book that had a race like this.