It seems to me that a good indicator of a healthy romantic relationship is that each person in the partnership notices and values the quality that the other person values most about him- or herself. Here's an example:
My sister Lexia is nice to everyone—the pretty, the ugly, the high achievers, the bums, the serious, the silly, the famous, the ordinary. It doesn't matter who it is, she treats them with respect and kindness. I think that's probably one of the things she likes best about herself. Her husband Adam once told her that that was one of the qualities that attracted him most to her.
This kind of attraction is important in two ways: 1) It indicates that each partner values the same qualities, and 2) It shows that a person's partner recognizes something that may not be obvious to everyone else. There is a specialness about that, I think—that someone notices the mostly unnoticeable. Or the mostly overlooked.
I suppose there are things that are valued and obvious, such as beauty and athleticism, but it seems like those typically aren't the things people like most about themselves. I think the "soft" qualities are the ones people value most in themselves, and if they find someone who values those soft qualities, too, then there's a good foundation for a lifelong romance.
Thing I'm thankful for: good lunch conversations