My favorite to play in- Planescape.
My favorite to run- Taladas.
My favorite to read about (but not sure about the playability)- The rest of Dragonlance.
Others I'm quite fond of- Ravenloft, Dusk, Dragonstar, Al-Qadim
I'm downright sick of the Realms, but I'm not going to turn into a realms-basher over it... I just want to play something different. Kingdoms of Kalamar and Scarred Lands don't hold much appeal to me... Dusk has been canceled, I'm not interested in running Planescape anymore, my Taladas box is in Pennsylvania (and I'm not getting it back anytime soon), and 3E Dragonlance isn't going to be here for another year...
Time to start building a new campaign setting!