1. It should advance the plot.
2. As a corollary to point 1, a perfect chapter should also contain something new to the story, something that makes the reader go: Oh, wow. In sff, it should stir that sensawunda.
3. It should advance the development of at least one of the characters. The reader should find out something new about him/her/them.
4. It should contain a mix of dialogue and action and description. (I realise not all chapters can do this – but I am talking about the perfect one, right?)
5. The tension in the dialogue should keep the reader on edge.
6. The action should make the reader read breathlessly, racing to find out what is going to happen.
7. The description should give the reader a picture of the surroundings that they can smell and taste and hear and see – and do all that without boring them.
8. The imagery should make another writer wonder why the hell they didn’t think of that first.
9. No passage in the perfect chapter should tempt the reader to skip a word.
10. The whole package should leave the reader panting for more.
And the perfect chapter I just read? It was in Russell Kirkpatick’s new novel Book 1: "The Path of Revenge" in a new trilogy (not yet published – but what a treat in store). Watch for this book when it hits the shelves. Russell's name is one you are going to hear a lot of in the future; his first trilogy was just an appetiser - he really gets into his stride with this one.
I’m about to go and commit harikiri because I am not sure I will ever be able to write something as good as this.