I'd mention my attempt at cloning a simple video game (Berzerk) that I started two years ago, which has only wound up with my having built, destroyed, rebuilt, scrapped and rebuilt an ECS framework, but technically I haven't given up on it yet because I decided I should just make Pong instead, because if I can't manage Pong then what am I even doing, and so I'm working on Lua bindings for SDL for ... reasons. Researc…
my most productive time writing games was using some proprietary scripting thing (dark basic), back when I didn't know how to do anything else at some point this degraded into "learn C/C++/OpenGL/direct x", which were good learning experiences, but the goal of making a game degraded into making game engines, none of which I ever finished.
I guess the moral of the story is that it's not really a failure if you learn something and keep your work archived somewhere.