I think it's a combination of the two. Assuming that you are needed by the person you want, and you need that person and that person wants you as well! If you want someone and that person does not want you back or does not seem to need you, it's a lonely place to be. If you need someone and that's not reciprocated either, again it's lonely. So the combination of wanting and being needed fulfills something in all of us, though I'd be dangged if I can put words to it.
Good QOTD!