I prefer the Forgotten Realm setting because there is such a wealth of fictional work to draw on. I mean if you read about, oh say, the Time of Troubles or Menzoberranzan in a sourcebook, it's like you are readin a high school textbook sometimes. On the other hand, if you grab a book by R. A. Salvatore or Ed Greenwood, you can read what it was like for someone who lived through that event or was raised in that area. This not only helps the players bulid a more realistic background and personality for their PCs, it also helps the DM create NPCs with more individuality than "generic dirt farmer #783". Also, some players get a kick when thier favorite fictional characters get a cameo in the campaign. Little thing like a passing reference to a moon elf crime lord known as "the Serpent" or a brief glimpse of a dwarf with green hair and beard armed with a club. Hee hee hee.