I fund it somewhat hard to decide on this but in the end LotR wind by default, really. D&D is both directly and indirectly spawned from LotR. My favourite pen and paper RPG is actually Icelandic so it would do dreadfully in international polls.
I'd like to see a poll between Eberron, Forgotten Realms, Dragonlance etc.
Well, LotR was around first, and is likely the world most fantasy realms today are loosely based on so there should be some measure of homage in any case. Though I have to give it to D&D. Why? Because of things like Forgotten Realms, which have been in development pretty the last thirty years. That's a lot of time and a lot of descriptive fluff to flesh out a world.