2) J.K. Rowling's Harry Potter series. Uh, duh.
3) Suzanne Collins's The Hunger Games Trilogy. I think this one is important enough to share with my kids.
4) C.S. Lewis's The Chronicles of Narnia. This is really the classic of children's fantasy, and I'd want my kids to at least read The Lion, the Witch, and the Wardrobe, if not the entire series.
5) A Wrinkle in Time by Madeleine L'Engle. If we're doing the classic of children's fantasy, we have to do the classic of children's sci-fi as well. Plus, this presents a fantastic female character for them to look up to, which is an important thing for both boys and girls.