From what I've read, the proposed mechanism behind literary fiction enhancing empathy is that it describes the emotions of the characters in a vague or indirect way, and working out their actual psychological character becomes plot-relevant. This was distinct from genre fiction, where the results were less obvious. So the 'good guys are always rewarded' bit, which is prevalent in genre fiction, doesn't seem like the best explanation for the effect. It could be compared to an extended story problem about empathy - at least as far as predicting motives and emotions.