While I'm not interested in making Video Games anymore, I do have ideas for some and still have them(For some odd reason).
One, is a Survival-Game. An extremely difficult one(We're talking about, the difficulty of Don't Starve here, but even more difficult). The Game plays out in a realistic-manner, so you're dead, you have to restart. Tasks take sometime to do(So chopping trees takes sometime), Crafting tools also takes sometime, you get the idea. Any Task can take sometime to do.
Pretty much, the entire Game plays out as real-life. You get mauled by a wolf, you either get killed by it or you somehow survive but start bleeding out. If you starve to death, you die extremely fast.
Of course, a Game like that would take an extremely long time to make due to the realistic-manner of it's Design. I'd be writing the Code for it for about 7+ years, not to mention that there is then making the Art(Textures) and Models, which are also meant to be realistic to fit in with it's realistic Mechanics.
Another one, is for a Post-Apocalyptic RPG Game. Just like the Survival-Game, this one is also extremely realistic. But with additions such as Radiation and NPCs. Again, this would also take an extremely long time to make due to it's realistic Design and Mechanics. Not to mention that it's an RPG. Were as the realistic Survival-Game would take about 7+ years to make, this would take about 10-11+ years.
But, as to where I got the ideas for these, I don't have a clue. They just came to me at the time when I was interested in making Games and have stuck with me ever since. I mean, of course, I don't have to make them 3D Games. I could simply just make them Text-Adventures(That shortens Development-Time drastically), but, I have to deal with things such as Player-Input with the Commands and all of that stuff.