While there is some merit to the selling base of Forgotten Realms vs. Eberron dispute, I do not see how that can be any worse than any roleplaying game that is not based on an established IP, and yet those pop up all the time. And I think that the D&D Logo has more to do with the success of games than the FR Logo. Which means that the only real thing keeping games based on other worlds from doing well is quality. It almost seems then that FR is just a crutch for developers who don't think that they can make a good game, because a good D&D game should be able to sell.