Eberron, the creation of Keith Baker, is the winner of the Wizards of the Coast's 2002 Fantasy setting search (They've only done this one). The entire setting is oozing with pulp fiction goodness: magical crime noir, rising international tensions in the wake of a “World War”, evil Nazi-inspired organization, menacing Cthulhu-mythos type creatures, and a whole bunch more. Needless to say it is (over-)loaded with potential story arcs. There is so much going on in this inspiring creation…So much that the idea of running an Eberron game is daunting.
For me, it is sort of a “kid in a candy shop” syndrome, too many choices and the brain shuts down. After all, Cthulhu or Nazis? How can you possibly choose? And how can I do it justice? There are too many things to remember, and even if I choose to forget them, there is a part of me that feels I should remember them.
Which lends me to prefer the collaborative world creation that is highlighted in Diaspora, Dresden Files RPG, and Burning Empires. Everyone involved in the campaign session is busy creating that world. Each participant in the game is mechanically allowed and expected to develop the world, and thus create a reflection of the players.