This is an old post I did somewhere else, but I thought it might interest readers so I’m editing it and putting it here.
The character must be relatable, interesting, or likable, preferably all three.
Morality is probably the most important thing in this department. I have trouble relating to characters who are immoral. I don’t like a character who disobeys his/her parents without just reason, or a character who constantly lies.
I don’t like perfect characters. Yes, I like characters to be moral but that doesn’t mean they don’t ever struggle. For example, it makes things much more interesting if the character is struggling with obeying his/her parents when (s)he is trying to save the world from some sort of apocalypse. (Note that in this case, the character should have a good reason for not telling his/her parents about the situation.)
I prefer the character be better than I am, or working toward that. I have trouble relating to a damsel in distress, or any other character who is more helpless in a situation than I would be. (I can like this character if they’re younger than I am, but I still have trouble relating.) If they start out as a damsel in distress, then grow as a character and learn how to take care of themselves, I can grow to like them.
I often like a character near my situation in life. It’s easy for me to relate to a farm kid who shoots varmints out of his aircraft and joins a rebellion than it is to relate to a city kid who has been trying to get on American Idol.
The main villain should be someone I want to see beaten or converted. If the hero is boring me, an interesting villain can help keep my interest. (Be careful with this. If the story is really boring, I might start hoping the villain will win just so something happens.)
Keep in mind that some people have different political views and could relate to the villain, which isn’t good. If the villain is a rancher trying to make a living and the “hero” being someone trying to stop the rancher from protecting his livestock from predators, I’m going to root for the rancher.
I like to make up my own mind if the character is good looking. I don’t like other characters constantly mentioning their looks. It tends to make me dislike the character. In the case of other attributes, the same goes. If a woman is a good fighter, instead of having other characters tell everyone about her abilities, I want to see her beat up someone so I know for myself that she’s a fighter.
A good plot with fast pacing holds my interest. I can sometimes overlook slightly annoying characters if the plot is good. (This part is more subjective and related to my personal preferences.)
A mystery is really fun. I like a good mystery in a book. Note that I don’t mean a crime mystery, but I like one where the identity of the villain is a mystery or something like that.
I love a good plot twist. If the book has a plot twist, especially if there’s a little foreshadowing, it really makes me interested.
I like to see lots of struggle for the characters and action. If I don’t like the characters, a romantic side plot is going to be really boring for me. (These often are only tolerable if I like the characters.)
The only romantic tension I’ve had much luck relating to is the kind that involves politics. (For example, if a princess is in a situation where she has to decide if she wants to marry a guy she doesn’t love, but she knows marrying him would be the best thing for her people, it’s interesting because she’s torn between her duty and her own happiness.)
I like the book/show to feel realistic and mature. The characters need to be in danger, and it has to feel like something bad could happen to them. With some books written for younger kids, the fear that someone will be hurt just isn’t there for me.
An interesting world helps. I’ve read a few books where I kept reading, just because the world was interesting but the plot and characters bored me.
If the world has lots of interesting cultures, I might want to learn about them. I like to see how different cultures interact, or avoid each other.
If there’s a bad species, I’m going to want to know why they are bad. I get quite annoyed with the idea that certain species, say goblins, are born evil, mostly because I don’t think a loving god would make an evil species that has no hope of salvation. Instead, it’s much more interesting if they’re evil because of their culture, or perhaps they’re misunderstood.
It’s a lot of fun if the world has a historical mystery. It’s always interesting if it turns out there were aliens visiting the planet, or if the character finds out their species is an alien to the planet.
Good descriptions in books or good graphics in movies helps me feel like I’m in the world. I once read a book that had beautiful descriptions of undersea life. It made me want to dive into the ocean. In movies, this is more graphics related, and since movies are more visual, I find graphics in movies to be more important to my enjoyment than tons of description is in books. In both cases, I’ve seen it overdone to the point the graphics or description don’t leave enough room for plot and characters so it’s a delicate balance.