Time to retire the hawk?

There's a little thread on RPG.net right now about retiring tired old settings that have lost their luster. Although it pains me to say this, I think some of my favorite commercial settings reached their creative zeniths a long time ago. Mystara, the Known World of my earliest campaigning, became cartoonier and cartoonier as the world expanded. I was never satisfied with the material expanding outside the original continental map from module X1 The Isle of Dread. Heck, some of the Gazeteers seemed uninspiring to me. The good old Grand Duchy of Karameikos stills works for me though. It's my primal example of a decent small campaign setting. My conceptualization of a large scale campaign rests firmly on the shoulders of Gary Gygax's World of Greyhawk boxed set, with a small side order of Tolkien via MERP. Almost all of my D&D games have been set in either the Known World or some part of Greyhawk. My most susccessful DMing endeavors have been set in one or the other: the D&D Basic/Expert game featuring my old buddy Dave as Axe the Hobbit-Hater rambled through Mystara, the 1st/2nd edition AD&D game featuring Pat as Doctor (later Baron) Phostarius was set primarily in Greyhawk's Bandit Kingdoms, my one go at a 3E game used Greyhawk's Blackmoor with an infusion of Arneson's original Blackmoor, and my nostalgic 1st edition game flitted across Greyhawk's Flanaess when a setting was required.

Still, everytime I set a campaign in somebody else's setting I hear a little voice inside my head says "Real DMs write their own setting." I feel like I'm cheating myself out of one of the most rewarding creative experiences in the hobby by not tackling the porject of writing anfd running my own campaign world. Even if it turns out to be nothing more than an intricate patchwork of derivative ideas, it would still be mine. I can't get that sense of ownership from Gygax's or Arneson's or anyone else's setting. I just need to figure out what exactly I want from a campaign world of my own. I've started the process of writing a dozen or more times and usually get no further a few pages of notes and a map. Without identifying exactly what I hope to accomplish and a clear methodology for achieving those goal, I fear all my efforts will end that way.