I think that classic novels hinge on certain things.
The novel should have universal meaning. Defining a generation, the story of the Boy Who Lived will hold meaning for years to come. The Harry Potter series deals with some universal themes, including the power of love and acceptance, and the idea that one small thing can make an ordinary person extraordinary. Harry Potter also serves as a reminder that bravery isn’t defined by an absence of fear but by the willingness to stand up for what you believe is right.
The novel should be timeless. The events of World War II have long since passed but Markus Zusak uses The Book Thief to find beauty in a horrible period of time. If nothing else, the narration in this book is something that will never get old.
The novel should have a moral message; it should say something about human nature. The reluctant love triangle gets a lot of focus but The Hunger Games has a deeper message: what things can you bring yourself to do in order to survive? And, once you’ve done those things, can you live with yourself?