One of the reasons I created Midian was that I only found the ultra-lite generics and barely-started unfinished works available on the 'net. Since I was making good use of free resources, I wanted to give something back for free. I knew I had the talent to pull it off, and the fortitude to stick with it. Had my google-fu been better at the time, I probably would have contributed to an existing game that was already further along. I thought about finishing one of the quarter-done ones, but I either couldn't get ahold of the creator, or would have had to do most of the work anyway (and would have preferred to scrap what little was there).
There's nothing inherently wrong with taking existing memetic space and making it your own. D&D replaced Tolkien well enough. And consider Along the Watchtower. Is it the original Dylan version you hear in your head, or is it Hendrix instead?