I had two big projects I abandoned for different reasons.
First was The Gladiator Project. It started life as a simple hack-n-slash for 2K, which was ported over to 2K3. It wasn't very well-known but still had a small following. When XP came out its entire storyline changed, but it was based in the time of ancient Rome, combining history with futuristic technology. There were plenty of plot twists and turns. Even the language was "Latinesque" (kind of like pig Latin), invented as "gang slang".
It was an ambitious project given that I knew very little RGSS/Ruby script. It was then developed for VX and was 60% complete, all custom graphics. I asked around on several forums how to do certain things script-wise, mainly to learn, not for the scripts themsevles. I was met with condescension and ridicule. And eventually lost the drive to continue with it. (That's the very brief history of its long and checkered past.) Eventually the project was dropped. I may rekindle it for MV after Otherworld is complete.
The second was Paranormality (actually a planned trilogy planned for each of the RPG makers - XP, VX and VXA). Life took me in completely different directions and I no longer had sufficient time to invest in the game development, although I did write the trilogy as novels. The concept was based on my own experiences in parapsychology and paranormal investigations, focusing on Jack Urban, a paranormal investigator, whose quest was to search for his sister. She disappeared under mysterious circumstances and Jack was convinced that she was still alive but in the "Otherworld".
I've rekindled this project for MV in the form of Otherworld, but it's a departure from the original concept while integrating much of the storylines from the trilogy. It's basically five stories in one, with added characters, plot twists, and concepts.