I have some ideas floating around in my head. (Ones that I hope to make someday. So my lips are sealed on specifics.) Biggest problem is - I can't code to save my life. Unless we're talking about doing very basic shit in RPG Maker. So I'd likely start with something more focused on writing. Maybe more akin to a visual novel than a game. (A thing I'd be better at.) And I've dabbled in music creation. So I could always "download" some programs again and try to make my own soundtrack. [i]Just be harder to do without the instruments and good microphone that I had back in ye olden days.[/i]

But I'd almost certainly want to incorporate mystery elements. Because I feel like a lot of mystery games / forms of media are very lazy when it comes to writing a good case. Because "writing quality" has generally been pretty weak in most modern games. So games that have good character writing often stand out to me.

But you definitely have to flesh out your own idea and "want it" strongly enough to create a game. Because it's a lot of time, energy, and likely a lot of watching YouTube Tutorials to do so.

If you have any game-making or coding experience already, I'd certainly recommend looking up "Game Jams". Because those usually give you certain topics and mechanical ideas to work around. That, and go play some more indie games yourself. Cuz there's plenty of free stuff on Itch.io or elsewhere. (Games on "Dreams" for Playstation can be very simple as well.) And that'll give you a scope that's a lot more manageable to inspire ideas of your own. 

Did you have an idea WHERE you wanted to build a game? (Like what programs you wanted to use.) Because that will also effect the kind of games you *can* make. And that sort of feels like the place where one should start.