That "fatal flaw" in this poll is that people are going to vote for one of their own worlds, because those are the only worlds they know. Nobody's going to vote for a world they used to play in, because of that world was so great, why did they leave? And nobody can really vote for a world they've never played in, because they have no first-hand experience to base such a vote on.
What this is going to come down to is a bunch of people posting "MY WORLD IS BEST!".
An interesting exercise at best, but I wouldn't expect any tangible or meaningful results.