I've thought about developing a game like Jump King or Getting Over It but in 3D. It would be pretty simple to program, mostly just making art assets. I don't really like that kind of gameplay though, which is why I never put effort into it
All the games I really would want to make are far more programming heavy, and I dislike programming a lot. Stuff like card games, simulation games, RPGs, adventure games, etc. The concepts I've thought up will have to remain as rough design documents.