What makes a short story great?

I never know...I think if you take the time and trouble you can figure it out in most cases but I'm too lazy.

This story really amazed because it's barely about anything and yet it's excellent.

Whereas this Dave Eggers story a couple of weeks ago was badly written and very boring. More high drama stuff and yet so much more empty.

I'm slowly trying to break my short story addiction. I was reading Yukio Mishima and didn't go crazy and stay up all night or anything. Again, why are Mishima's stories so great? I can't say precisely. Sometimes they are bizarre and not much of anything goes on. Or long, long descriptions of a single action make up most of the story. They are focussed and gemlike and perfect. Although the gossip about him is that he was an egomaniac (and crazy in a number of ways) his ego is absent from his stories. Only the characters come through. They have this...purity.

But that's all metaphor. I think there must be some mechanics involved as well. Clean sentences and so on.