The concept of “liking a character” can be separated into three categories:
- Admiring the character on a moral level. That is, thinking that the character is a good person.
- Liking the character on an emotional level, but not on a moral one.
- Disliking the character as a person, and nonetheless enjoying reading about them.
The characters that fall into the second category are people that charm you in some way, even though you consider them immoral and would not actually like them as a person. The obvious example – Hannibal Lecter. We all know Lecter is evil, but his evil is not self-righteous or banal, merely self-serving; he's charming and intelligent; he has a system of values that makes vulgar, rude people likelier to be eaten; he values politeness and intelligence.
Finally, the characters that fall into the third category are people you wholly dislike, on a moral and emotional level. For me those would be the stupid, the willfully ignorant and self-righteous. Basically, people who are evil in the banal kind of way. Let's say, the mother in The Virgin Suicides.
But even the latter can be an engaging and interesting subject, if they are what any kind of character needs to be, to be any kind of worthwhile:
A real person.
And this has more to do with how masterfully the writer crafts them, how expertly they create a human being out of nothing, than with the particular specs.
A reader doesn't have to like a character to like to read about them. If they feel overwhelmingly real, they'll pull in the right readers. The rest is a matter of taste.
When writing a novel a writer should create living people; people, not characters. A character is a caricature.