What do you think makes a good story?
Perhaps that's overdoing the metaphor a bit (or a mile), but that's the truth of the matter as I understand it.
A good story follows a natural outgrowth of the characters' choices, both action and inaction, and takes them on a roller coaster of emotional and physical and psychological ups and downs. A good story changes the characters in it (all of them) for good or bad. They become better or worse. A good story doesn't allow them to be the same person at the end they were at the beginning.
On a personal level, I define a good story as one that doesn't give me the option of putting it down nonchalantly. I should have to wrest it from my hungry hands and force myself to get on with the other stuff of life because I care so strongly about the people whose lives I'm following.