Oh, goodness. I know in advance I'm going to sound like the most self-righteous prick on the face of the Earth (and the muffled voices commenting it would be nothing new can go eat pineapples: I'm going to be
worse than usual, that's what I'm saying). Please, Villain, understand I don't mean to. I have no truths to impart, your way of living your life is as good as mine and possibly a lot better.
Villain said:
However, if I now change it to: "The woman of my dreams wants me to move to Australia with her, promising to love me 'til the end of my time." - the result will still be the same. Granted, I'd probably try to discuss the matter and suggest other possibilities ("You go there and I'll visit you every holiday") now that she isn't actually blackmailing me. But in the end it would all be over. I can't imagine a woman who'd be worth it - and I can imagine quite a lot.
Well, this makes sense to me. You're not willing to move to Australia for no other reason than the possibility of an ever-lasting relationship. There's no need for a woman to be worth something like that for love to be a feeling with some - or a lot of - merit.
I'll try to clarify: separate the idea that love implies sacrifice from the idea that love implies pointless, gigantic sacrifice just because. It's pretty much a done deal that if you're not inclined to move anywhere without a reason founded in your job or interests, then you're not going to spend all eternity with an Australian gal who's likewise not much in the mood to travel. Should you fall for one, well, too bad, let's move on to the next.
This is highly subjective and - a little like what I was talking about with Tritonus - a sign that love can hardly survive on its own, in an empty field where you
first decide you "totally omfg ^_^ luuuv" her, and
then proceed to change your desires/habits/personality according to please her. It should really be the other way around: when you meet a girl who seems to be in tune with what you like and what you're aiming at in life, then you open up a door and maybe decide it'd be nice to share more with her. Share things you wouldn't share with a friend, make plans for a situation where you get to pursue your interests together - for instance - because, frankly, it's a tad more pleasant.
What then is the real content of love?
I'll tackle this answering each question/hyopthesis of yours, because I can't express anything exhaustive as an answer. Of course, I don't know either. I don't know anybody who does. You probably approach the subject by proximity, or by at least ruling out what you absolutely do not want to be the content of love.
but I have kind of thought that love is all about two persons' emotional dependency of each other
No, no. That part is unintentional, and best kept to a minimum. Of course there is emotional interaction, like reacting to each other's moods and being sensitive when it comes to how your significant other feels. But you want to avoid being a sad sop who screams "OH MY GOD DID I HURT YOU???" and hit your head with a wooden stick every time you accidentally step on her foot.
the feeling that you want to be with her all the time,
Maybe, and maybe not. If you two want to be with each other all the time, more power to you, hope you share at least the same continent. If you are ok with taking some alone time, or time spent with friends who are not mutual every once in a while, that's healthy too. There's no set rules aside from a certain proportion in the way both people involved feel.
you want to make her happy even if it costs you much,
That's more like it, yes. But I don't see why this part seems to scare so much a person as giving and selfless as you, Villain. It's really not that different from wanting to provide and help others. We're really not talking happy as in receiving bolts of adrenaline to the chest every second she's with you. Just, you know, the normal stuff only with a bit more fire in it.
you want to make her the gravitational center of your life, forcing everything else on orbits far away.
For the first part, see the "spending all the time together" answer. The second half of this statement sounds a little morbid if you ask me. There's no rule saying only because she's more important than other things, other things will have to disappear. If your interests are so pervasive that they take up all of your time, then it's true that you don't need love in your life (at the moment), but it's not because it's love that's unnecessary, it's because you have other things on your mind.
And that leads to neglecting all the truly important things in life (which would in my case include friends, roleplaying games, volunteer work, anime, DT, internet forums, etc).
For instance, my current girlfriend (a) goes out with my friends when I do (and I with hers); (b) is working just around the corner of this office right now (while I write on forums instead. The joys of slavery!

); (c) likes DT as much as any person with a brain should; (d) frequently reads a couple of websites I read as well (in fact, we read them together); (e) is interested in my hobbies and the things I like enough to show that she's not either dragging her feet or overly enthusiastic just because it's her beloved rahvin telling her they're great. This is after less than three months going out together. I don't really feel like I'm
neglecting important things in life. I'm probably neglecting things that were really not that important to begin with. Too bad. I'll pick them up again if I ever feel spending time with her is not worth it any longer.
What is it that I would gain in return? Someone who is always at my side when needed?
Perhaps, but it's not as if you plan to give your significant other vast amounts of your time so that one day you'll use them for a crutch. It's normal that, among people in a successful relationship, moments of uneasiness are faced together and with much support given and taken. Achieving that, however, is really not the reasoning behind the masterplan of all us geniuses who choose a family life: it's a consequence of caring.
Someone to share my moments of joy and pain with? Again, there's plenty of such people.
Again, as above. It's great that you already have people who, apparently, fill your emotional needs (or wishes), and it's also great that you don't really want to find a girlfriend to cure your loneliness. Still, this idea is superficial and more typical of the kind of people who don't really look for
much in a companion, except for him/her to be there and share the misery. You're more in the category who might want a partner in crime, no matter the crime.
I'll post a second part later, I gotta rush right now.