In their capacity as literature, the texts of the Bible aren’t exclusively of religious concern. (That’s hardly an original or incendiary suggestion.) So perhaps you’ll find this reading of Cain and Abel — found in a review by Shalom Carmy of a book by Rabbi Lord Jonathan Sacks — worth a few moments of sunny Saturday contemplation:

… the rejection of Cain’s offering is one of the most puzzling features of the story of the first murder. Classical exegetes, Jewish and Christian alike, have ingeniously found reason for God to discriminate between Cain’s vegetables and Abel’s fatted lamb, although their arguments seem to read more into the text than is manifestly there.
As a result, many modern readers have realized that Cain’s response to God’s rejection matters more than the perfection of the sacrifice. I don’t think anyone has expressed this better than Sacks. He looks at the offering as a gift. When a gift is rejected, there are two possible reactions: If you, the giver, ask what went wrong and try to do better, “you were genuinely trying to please the other person.” If you become angry with the recipient, “it becomes retrospectively clear that your concern was not with the other but with yourself.” This combines a profoundly satisfactory reading of the text with a powerful moral lesson.

Our culture tends so strongly toward a rejection of overt (as opposed to insinuated) authority and an embrace of self-centricism that it takes a moment to adjust to the frame of mind that the reading requires. We tend, that is, to find an initial inequity or unfair treatment largely to exculpate the reaction.
Was God’s preference for Abel’s gift arbitrary? Cain doesn’t take the path toward finding out. He judges his gift by his own criteria and determines himself to have been wronged. As much as we may unite in lamenting his ultimate remedy, it’d be difficult to argue that we don’t take a similar approach in such wide venues as personal interactions and social governance.