I know it's going to sound silly.. but I'm a big believer in personal energy. It's a little like auras or chakras, but without all the ancient asian mumbo-jumbo to get in the way.
I think that different people have a different "intonation" to the natural vibe they give off. When you meet someone in tune with you, then you get a good feeling from them. And vice versa. Some people have a more compatible "tone", so more people start out liking them. And again, vice versa.
It's all in the mojo, baby!!