Saw both Hunger Games movies this weekend - first one on Netflix before seeing the second with family. I thought Catching Fire was MUCH better than the first. I didn't feel for anyone until Rue was killed and Katniss broke down. That was the only relationship I felt was compelling in the first one, but the second one was a lot better in establishing relationships through interactions instead of assumptions. (I haven't read the books, but I believe you shouldn't need to know the books to appreciate a film adaptation.)
I also welcomed the addition of Jena Malone and especially Sam Clafin. But Jennifer Lawrence definitely MAKES these films. They wouldn't be the same at all without her. Such a natural talent.