I’ll start with my current character because he’s the freshest in my memory. A year or two ago, we decided to move our ongoing campaign from Faerun to Golarion. The current arc is based in the deserts of Osirion, running through the Mummy’s Mask and related modules.
Hands down my number one all time favorite is 1st and 2nd edition Krynn. 2nd favorite is 2nd and 3/3.5e Forgotten Realms. I have to admit, though, that Pathfinder’s Golarion is starting to grow on me.