I couldn't tell what kind of RPG you were talking about, but I've made both kinds.
For pencil and paper games, I've made several. I'd make and gamemaster (GM) a game for my friends. Each one
was uniqe in its approach and genra. I made a percential-based "Three Musketeers" game, a D20-based spy game
based on an Earth history without large scale wars, and a D-10 based body-mind-spirit game where everyone was highly
magical.
Taking all the things I learned from my previous games, I made a game system that I really like. It is exceptionally
well balanced, no matter what kind of character you play. It even prompted one of my friends to say, "[Dang] it,
how am I supposed to munchkinize my character!"
My friends also asked my if I wanted to try selling it to a game company. I always said no, though. I figured as soon
as money comes into the system, it wouldn't be fun anymore.
For computer RPG's, I never made my own from scratch, of course. That would take way too much time. But I do like
making game mods for Neverwinter Nights. The world I've spent the most time on is based on the Anime "Rune
Soldier", aka "Louie the Rune Soldier". The world I wrote takes place immediately following the end of
the events in the Anime. It's not complete by any means, but I have written quite a bit. There are stores in
Ohfun that sell almost anything you can find in the main game, plus a few custom items. To keep my friends occupied
while I keep writing onto the world, I built a monster maze, full of baddies just waiting to be killed. The Tartious
Forrest is a fun place to hack as well. There's no big story line just yet, but I have hidden some fun, informal
side stories in here and there.
Well, that was a long answer to a short question. Oh, and if anyone is interested in any of my games, just let me know.