The first truly long-term campaign that I ever GM-ed was an AD&D 2nd Edition game that ran from my sophomore through senior years of college. For this game, I used Arcadayn, a homebrewed setting based on an idea from a high school friend. After college, I kept tinkering with the setting, and once I got hooked on GURPS, I started converting the setting to that system. My GURPS GM had done just that with his old D&D world. One advantage of this system change was that GURPS was easier to customize, allowing me to overhaul the setting in ways that removed or reduced some of the most obvious D&D-isms, making Arcadayn into even more my own original creation.
After a few short-lived attempts at running Cthulhu Mythos adventures using GURPS, some of those players expressed interest in playing a "pure" fantasy campaign in that system. I took some time to develop my new version of Arcadayn to the point where I was ready to run something in it, and created a website in order to share background information with my players. That game was very successful, running for over 50 sessions over three years of regular play (from 1999 to 2002). During that time, our three young heroines forged a deep friendship that transcended their very different cultural and religious backgrounds. Their accomplishments included defeating a vile necromancer, befriending a dragon, and rediscovering a long-lost divine artifact that had been broken and corrupted by evil deeds. When one of my three core players could no longer make the time commitment due to her demanding schedule, we found a stopping point to the campaign that provided definite closure (purifying the artifact, and facing down its defiler's revenant) but left open the possibility of returning to those characters at some future date. (Sadly, that sequel never came to pass, and we no longer all live in the same state.)
A couple years later, I resurrected part of the original Arcadayn setting from my college days for a D&D Third Edition campaign, but I put brand new twists on this version (which I dubbed "Ursk"). This game was soon put on indefinite hold when my wife and I became parents for the first time. When we were finally able to resume gaming later that year, we chose to return to one of my other campaigns (Freeport) instead.
Since then, I have continued to putter with Arcadayn. When I had to move the campaign website to a new home in 2007 (due to GeoCities ceasing to be), I borrowed an idea from Green Ronin's Freeport setting. The company had relaunched that line as a series of systemless setting books with separate companion volumes for playing Freeport in different systems. I organized my new wiki to present the background information in systemless form, with the GURPS material on separate pages. I had acquired GURPS Fourth Edition by that point, but had not had an opportunity to play it, so I added some Fourth Edition conversions. I had also toyed with the idea of converting the setting to BESM Third Edition, so shared that new information there as well.
When I had to migrate my various gaming websites to a new home about a year ago, Arcadayn's was unaffected because it was at a different host. However, I've decided I prefer Google Sites over PBwiki, so I've just finished copying Adventures in Arcadayn to a new wiki there. I had not looked at any of this material in a very long time (since shortly after the last migration), so this task set me to thinking again about what system I might use if I ever run another Arcadayn campaign. I haven't played GURPS since we wrapped that first campaign. While I would love the opportunity to finally try out GURPS Fourth Edition, my group--which still includes two of my Third Edition players--prefers very different systems these days. Our current default system is Pathfinder, after a decade of D&D v.3.5 holding the top spot. Arcadayn has changed too much from its D&D roots to be easy to convert back to any edition of that system, but I might be able to use Pathfinder to find a playable middle ground. A more generic system would allow more flexibility in character creation, which was one of the main reasons I used GURPS last time. Of the multi-genre games I've played, BESM Third Edition seems the best choice. It has the wide variety of character options I'd need, the rules are simpler than GURPS, and it's geared toward a more "cinematic" style because it was designed to model anime, not gritty realism.
Of course, I'm unlikely to start a new Arcadayn campaign any time soon--I simply have too many other games demanding my attention. I will, however, continue to tinker with the setting, as I try to model some of the setting's races, magical traditions, and character archetypes in different systems. (For starters, those BESM conversion notes are far from complete. And my Kynthiad campaign has generated a lot of new BESM material that I could adapt.) I'll post the more interesting experiments to the new wiki, and discuss some of them here.
(An older version of the history of how Arcadayn came to be can be found here.)