This post hits home for me because I've always felt the same way. No, I don't think that anyone is "better" than someone else -- I believe we're all valuable, obviously, and I think you believe that too. It's just an objective observation that one person may be more attractive, more intelligent, more...something than the other. It doesn't necessarily mean your self-esteem is low (in fact, from the way you wrote your post, it doesn't sound like that at all to me, but that could be because I can relate to what you're saying). It's tough for people to understand if they're not in the same position.
I don't believe my husband is necessarily more intelligent than I am -- we both are highly intelligent in different areas, but we both are strong in most areas (he's a math teacher and I'm an English teacher, but I have decent math skills and his grammar is better than most people's, for example). The inequality lies in our looks, and not just because of my weight. I was very heavy for a long time, but that's almost beside the point. I'm ok looking -- I have moments of beauty. I think everyone does. My husband, however, is generally considered very good looking by most people. Kind of strikingly so, and effortlessly. He doesn't think we're a mismatch in that sense, but I do. It's not my low self-esteem saying that -- it's more like my sense of reality! For example, when Julia Roberts married Lyle Lovett a long time ago, there's a reason everyone was surprised. I'm sure his personality was fabulous and they fell in love and blah blah blah, but noticing that she's more physically attractive is just natural. I don't think the disconnect is THAT obvious with me and my husband, though!
Of course it's all subjective and meaningless. I just wanted to tell you that there's someone out here who knows exactly how you feel! We've been married nearly 15 years, though, so it's working anyway!