I don't know anything about Battle Royale, but I did read the Hunger Games books when they came out. My kids were at just the right age and were reading them, and I generally tried to read what they were reading so I would be "in on it" and also so that we could talk about it.
90% of the time movies are simple-minded and lame compared to their source books, and Hunger Games was no exception (although I will say that the Harry Potter movies were considerably more successful than most). Woody Harrelson and Donald Sutherland were pretty well cast but I think that the films overall failed miserably to capture the bleak atmosphere of the books. In their defense, I don't know how you could really capture the despair and hopelessness that the books created in a mere movie.