Do you love the characters because not many people do and you feel sad for them or do you genuinely like them as a character?
I guess it depends on the fandom? Like, Percy, I thought he was cool but no one liked him so I made him my favourite character. Over time I have grown to love him, properly, and he is genuinely my favourite character now. (he's the only character I've got the official wand of, lol)
But Gabriel? Like anon pointed out, he's not a good character. There is no reason to like him, but yet I love him with my whole soul.
Mycroft (from Sherlock) is a well known character, but he's never considered a favourite. He's a right pretentious asshole, and I hate people like him in real life, but I love *him*.
I guess I don't know the answer. But its also why I don't have a "favourite" character in spn yet, bc I haven't actually evaluated the fandom, if that makes sense?