Maybe someone you like is someone who engages you. They make you want to interact with them. I dunno if that's any kind of insight or just "duh, that's what likeable means". But if I think about the people I like they're people who I want to know more about. That might just be what I find likeable though. It's like a fascination with someone. Kind of like being similar, but not necessarily like-minded because it's not unusual to find someone different from you likeable. Maybe it's also an appreciation, at least when you know a little more about someone. You see some quality in them and can appreciate the importance of it in their lives even if you don't have that same quality or even care about it yourself.