1. Believable characters (no matter how magical they are. There should be something about them that resonates with a reader, which is why magic is NOT the be all and end all situation to your characters' problems. There should be things for them to work out without magic. There should be things about their character which engage the reader so if the old fairy godmother turns up and does work magic for them, your readers are going to be pleased for them rather than see it as a plot device to get your character out of trouble!).
2. Emotional impact. Whether this is where your reader ends up screaming at your character to stop being so stupid or laughs with them or cheers when they get their happy ever after, as long as there is some emotional impact, your story is "getting through". People will want to read more.
3. Justice will out somehow. This is true most of the time. Stories where the villains win always make me feel uncomfortable. It just doesn't seem right. This is why I love the cliffhanger ending in The Italian Job with Michael Caine. Even where the villain does seem to get away with it, I like to see some hint that in the future their success may come back to haunt them or they would have done even better had they acted better. I suppose one reason why I like to see justice of some sort being done is because in life, it so often isn't like that. One appeal of stories overall is that they can reflect life as it should be at times - the underdog does win out, wrongs are put right etc etc. (The other thought here is that perhaps the villain does have cause so are they so much of a villain after all? Food for thought here I think).