A friend of mine worked on a horror game that was released last year - Home Sweet Home. This game is developed in Unreal Engine rather than Unity. In fact, they switched from Unity to Unreal as Unity was not performant enough for visual they were targeting, I heard. They are not targeting mobile platforms however.
If you happened to be from a country with quite rich culture (like me, which is Thailand), you will find some interesting story that might not be very well known internationally. I think you can start from that and expand it to area like game play, story, etc.
In fact it doesn't have to be folklore. For example, my ex-colleague told me once that his home town is the place where Texas Chainsaw Massacre took place. That can be pretty interesting as well, don't you think.