So a few years ago two of my friends and I created a fantasy campaign world known as Tarna for a proposed D&D 3rd edition game. We ran into problems when we got into the game only to realize that we weren't really enjoying the system that much. 3rd edition is great for some folks, but we were all too busy and too lazy to spend the amount of time that the game would have demanded. We ended up converting the game to a Basic Roleplaying variant we cobbled together, and this second attempt at the campaign was much more what we were after. Chaosium's Basic Roleplaying system is brilliantly intuitive system that worked well and provided us some memorable and gritty combat. I now realize that Basic Roleplaying has its limits as a system as well, but it worked well enough for us at the time.
However, we loved the little campaign world we'd created, so we kept adding little bits to it. We kept adding, brainstorming, and adding more. We were off dreaming up this world under the heady spell of Peter Jackson's Lord of the Rings films and about a million other things. The stuff we came up with rocked, but it had one little drawback: it was never going to come into the game. Looking back it was one of the most important lessons in my gaming life. It really taught me that while worldbuilding can give you great stuff--you can also drown in it. And we were drowning. Eventually, we moved on to other games having absorbed some of the lessons of our Tarna experience. Yet I keep looking back on that stuff wondering if I should still do anything with it. I've been tempted on a few occasions to run it as an old school OD&D campaign, but the best thing I got out of the Tarna campaign was a stronger sense of what works in the GAME not in some massive fictional world you keep tinkering with.
Some interesting features of Tarna:
* Elves were very long lived, mystically potent, and had held the people of Tarna in slavery for several hundred years, but were now mostly extinct (although they'd left behind massive tomb complexes).
* Goblins were a "plague race" that infected people and turned them into goblins.
* The planet itself was a living deity.
* Magic was an aberration created when the chaos planet Umaen hurled a piece of himself into Aeos (the planet the land of Tarna was located on). This shard of Umaen was the locus of mystic energy on the planet and located far out in the ocean stabbing like a knife far into the atmosphere.
* The savage war goddess Shiara had the head of boar.
Here's one of my maps: