Honestly, that's a pretty solid way to judge character if you ask me. Think about it, liking the "Dark Phoenix Saga" might mean they're into drama and self destruction. On the flip side, preferring "Days of Future Past" could show they worry too much about the future. From what I've seen, people's taste in stories tells you a lot about how they see the world. You might be onto something, even if it's a bit silly. Just hope your date doesn't pick a villain's origin story as their favorite.