Planescape and Greyhawk leading the pole is not too surprising. Eberon edging out the Realms, putting it in 4th place, and Dragon Lance in last place, are a little surprising, but voting is still early.
I voted for Al-Qadim, which had the most consistent quality of just about anything put out by TSR. Greyhawk, the Realms and Dragon Lance all had there high points, usually early, but are long past their prime. DL's massive changes over the years are probably one of the main reasons for its poor performance on this pole.
But for my "favorite D&D setting", see the sig