Love Exists?

Is there a definition for Love?
1. Someone watching your every move. Following you around in awe and finally proposing. You are forced by the admiration to accept him.
2. Someone with a more direct approach.  Who proposes within days of meeting, and if the feeling is mutual, the relationship moves forward. And it does!
3. Someone likes you and admires you and finally manages to talk to you. You take your time in deciding where to go from there. You choose him.
4. Someone finds you attractive in a party. Approaches you for a dance. You agree and within minutes he sweeps you off your feet with his charm. You are in awe of him, and things moves forward.
5. You meet a prospective groom in an arranged marriage surrounding. You can pick and chose the qualities you want. And you do!
6. Someone notices you and considers you worthy of marriage and approaches your parents for your hand in marriage. You get to agree or disagree. You agree!
7. You meet up with someone, friendship happens which slowly converts into a relationship and then into marriage.
All of the above are arranged marriages in a manner of speaking. Because you get to chose and decide. Most love marriages are decided too. It all depends on the people involved. If they have the guts to move ahead even under pressure from the families, they do. Otherwise it becomes a love tragedy.
I am curious to know which particular category above has the least failure rate. What it is that actually keeps the love alive. I am referring to love here and not marriage.
I wish I could do a census on this and make it aware to everyone I love and care about. What is the right way to choose a life partner? Is there really one? Or is it all by chance and fate.
I wonder!