How can we be friends?

I have this friend. A guy.

At one point we thought there might be more between us than just friendship.

Before I go on, I like to point out that this is totally my side of the story.

After a while of really getting to know each other, having fun and flirting, I knew it wouldn't work. He didn't. It was in early stage so nothing too damaging happened but I have a feeling he carries some kind of resentment towards me for not... I don't know what. Falling, maybe?

At first it was okay. He wanted to keep everything as they were.

I couldn't because it wasn't the same anymore. So I took some distance. He didn't appreciate it and we ended up creating far more drama than the situation required.

So I moped. That's what I do. I burst first, then pout, then crawl back. We talked and everything seemed to be fine. Not good, but fine.

Then I made the mistake of telling him I might be interested in someone else. And again I didn't take his reaction very well.

Lately I've noticed that he never takes the initiative to contact me. He barely says hi to me anymore. I asked him if he was mad, but he says he's not, he is just busy.

I also get the feeling he doesn't really appreciate the new friends I've made. He seems jealous even though I try to tell him that no one could take his place as a friend of mine.

I talked about the situation with my mom because it really bothers me. She said jealousy is something I shouldn't keep around in my life and maybe it would be better to let this friendship go.

So now I'm in a cross-road. Do I let us drift apart, do I tell him to piss off with his tantrums or do I fight about it and wait until the scars of affection has finally faded away?

What is friendship? What makes us friends to each other? Is it worth our time as it is, or should it be something special? Can we be friends with someone just for the sake of being friends?

How much are we willing to do for a friendship?

And the age old question: can guys and gals really be friends?