Likeable Characters

I have a question for you! Something I've been pondering lately...

In the past half year or so I've read a young adult book and an adult book that deal with the main character cheating with their best friend's boyfriend. In both cases, the best friend was portrayed as insecure, needy, bossy, and selfish. Not to mention that she treated the main character pretty horribly.

So, as a reader, I rooted for the main character to get the boy, despite the fact that she was betraying her best friend. She would claim that her relationship with the boy was deeper than the best friend's relationship, and of course I believed it, because that was how it was presented.

As I read the second one though, I began to wonder - how would I feel about this main character if the best friend were kind, considerate, and selfless? Would it affect how much I enjoyed the book?

I don't think I need a likeable main character to like a book, so long as the character is complex. For example, I loved Lauren Oliver's Before I Fall, and I didn't really care for the main character as a person for most of the book. She was exactly the sort of person I would have disliked in high school. But she was multi-faceted, complex, and - ultimately - she changed. She recognized the ways she was unlikeable, and she grew throughout the book.

I can't decide if I'd rather read a book where the main character cheats knowing her best friend is incredible and just owns up to it, doesn't try to defend her actions by claiming that, in some ways, the friend deserves it. I think there's a good chance I'd be incredibly frustrated with the main character. But I also think that in many ways it will feel more true, more honest. I'm sure not everyone who cheats with their best friend's boyfriend does it because the best friend is actually awful and deserves it.

So what do you think? Do you need likeable main characters?