I'm attracted to a lot of different things, but I think characterization is probably the most important for me. If I feel interested or connected to the characters then I want to know what happens to them, even if the plot is not filled with twists and turns. When characters feel like real people and I find myself wondering about the "rest" of their story and what they would do in other situations, that is a good story.

Of course, any story where you NEED to know what happens next is a good one. 

Well-drawn characters, a clever and (hopefully) unique plot, believable dialogue, comic relief, and a surprise ending (especially in a short story) will usually keep me reading from beginning to end.

It's absolutely got to have a well-developed, life-like character. Preferably more than one character who fits that description. Plots with twists are nice, but if I don't feel some sort of attachment to the character the plot doesn't matter to me. I could enjoy a plotless character sketch if it was well done.

Your thinking is in line with mine to a great degree.  I love well developed characters, action, an intriguing plot, unexpected twists, and a strong ending that isn't necessarily happy.  Sometimes it's hard to define what makes a good book, but any book that can draw me into the role of the main character will always great in my opinion.

The most simple mode of defining a good story, I think, is to say that a good story poses a question then leads you/the reader to the answer. 

This method of story-telling is used across all kinds of literature, from genre fiction to the literary fiction.