First attempt made it to three chapters before I decided it wasn't worth going further at the time ('81 or '82, so I was about 14).
First attempt I finished was a pretty blatant mashup of Lord of the Rings + Dragonlance + generic video game tropes justifiably rejected by the only agent I sent it to. Unless an ex-girlfriend still has a copy, it no longer exists anywhere as far as I know. That was my fourth attempt at writing a novel (three fantasy one horror IIRC). The others were abandoned for various reasons, no longer remembered. One of them (dark fantasy) may see light of day if I can bring one of the ones on Pocket FM to conclusion, as I had some ideas how to get around the main hole in the story - but that's about a year out at best.
In the 90s I was part of an Amateur Press Association based around a superhero RPG (Champions) - most of the stuff from that era, except the website I used to store graphics created for some of the stories, still exists in print copies (and one member of the group digitized the whole thing though I couldn't afford the DVDs at the time). Had a lot of prototype serial fiction there, including a bunch of stories set on a version of the world of True Blue - and, in fact, I started writing that as the script for a comic book one character was reading to her siblings while babysitting, but never got that far in her story. The concept for that world was that the stories were all set in a "near future" (around 2000 at the time), but the world had possessed superheroes since the '40s. They had their heyday in the 70s, and then an alien invasion happened around 1980 - the resulting war pretty much reshaped the Earth and had most of the supers, good and evil, either dead, retired or permanently sidelined in other ways before the world was freed. Now, twenty years later, superheroes are reappearing... It was a shared world project among an invited group of members (I was in the second wave allowed in), with a goal of having the writers meet at conventions to actually play their characters for games, but that goal never happened to my knowledge.