The meaning of friendship?

Dunno where to begin. WARNING, this may get into a life story.

I suppose I've never really considered what friends are before, or thought that I've really had them. I know what friends are, but what they do and make me feel like has always been a bit confusing. My autism makes me feel quite detached from people. I think it means that however close I am to people, I feel like I'm not quite with them. Could be also because I'm not that social, I'm shy and I have low self esteem, and my interests aren't quite mainstream. Recently however things have come to a head. I've put a 5-year best friendship on hold indefinitely at the request of my friend who I keep having disagreements with. She rightly said that I've become addicted to the feeling of importance I've got from her friendship and the need to feel like someone, as well as being unable to "accept" anything "less" than the "best spot". I do care about her a lot, and I know I've hurt her in the past. She believes that friendship tiers really don't exist, and I'm struggling to accept that.

I've noticed a pattern though. In the friends I have been able to identify throughout my life, I've always bounded myself to them very strongly, and the friendships have all ended miserably. In every case I've needed something from them that I haven't been able to provide myself--self worth. As a child I was very detached. I was interested in planets and dinosaurs obsessively, and was very intellectual for a kid my age. I struggled to make friends, and those that I did I attached myself to as I've said before.

People say it's not bad to be best friends with someone who doesn't consider you a best buddy (though they still think of you as a good friend), but for me that leaves a bad taste in my mouth. I've been there before: in primary school I was best friends with a boy, who wasn't best buds with me back. Sure, he liked me, but when there was trouble he would always run to someone else first. I really liked the guy, but he "just" liked me back. And because I was shy, I didn't even know how much so. In secondary school I was bullied. Not as much as I thought I was at the time, not knowing what bullying actually WAS, but it still left scars. I thought I had found good friends there eventually after a while, but after a disastrous party those relationships collapsed.

And what a long term friend of mine said to me last summer has also left its mark. She wasn't that excited to see me when I came to see her (though she was pleased I was there), in fact she told me the reason she wasn't that excited was because I wasn't her best friend. Is that a fair comment? I feel as much as people are totally welcome to like other people more than me, I would feel insulted if they told me that to my face, and act as if the "party only starts" when their best buddy walks into the room, no matter how long I've been in it.