That is a genuinely hard question to answer.
Good fiction has presented problems in such a way that it changes the way that I think about them. Or at least it makes me stop and think about whatever issue they're presenting.
Bad fiction is just run of the mill for lack of a better way of saying it. It doesn't have any substance to it.
I think that's the vibe I'm getting from this thread. Good fiction speaks to you in a way that is aligned with your own experiences. We all have problems and good fiction offers answers in the form of stories of how those answers could play out. And you could possibly apply that answer to your own life.
A good example for me is the book Stranger in a Strange Land. A human raised as a Martian, learning to be human again.
