Ron
Explorer
I usually homebrew, but my last campaign was set in Greyhawk. I personally like to run games in Greyhawk as the world is much less detailed than other alternatives. It is easy to pick a region and develop it to my liking, not being worried about players complaining that my game is diverging from something written in a official book. Also, unlike the Realms, I feel a sense of history and geography cohesion in Greyhawk that facilitates working with it.