I definately think it's more important to love the person.
In high school, my first "love".... We went out for a long time and eventually I realized that what I liked about her was that she liked me a lot, thought I was cool, was one of the first girls to ever show an interest in me, and she was cute, but that wasn't enough to base a relationship on. I realized that there really wasn't anything directly about her that I liked. She was quiet and didn't really have much on her mind, so she was just kind of like a presence.
I think a lot of the time when people treat their partners badly, it's because they really don't have feelings for the partner, but they like that the partner likes them. And showing someone how much you like them, usually isn't going to make them like you more. I'd rather someone show me why I should like them rather than showing me how much they like me.
The main thing is that there has to be a balance in the relationship of how much the two people like eachother. Two people who like eachother a lot can work, even two people who are only luke-warm about eachother can work, but if one person really likes the other and the feeling is not returned, it's not going to work. "I can love enough for the both of us," just doesn't work at all.