There are some great posts here already, so this may repeat some things already said.

I feel a good story needs believable characters, a story line that makes you want to read more, emotions to create a tone or feeling within a story and a logical order that lets the story flow.

I also like a story to have some background, so that you know where the characters are coming from. The thing though that makes a story go from good to great is the ability to make the reader forget all else when they are reading it. Hopefully, doing all of the above will let you come close to achieving this.