Adolescents are terrifically fascinating and terribly complex human beings. Kids, still, but also nearly adults and wrestling with all kinds of very difficult questions, ideas, and emotions. Katniss herself is in this age group, yet she is really not a very interesting or complex person. Her life seems to boil down to: "how can I protect my little sister" (whose death is about the most predictable, shallow, liberal cliché on the futility of war imaginable) "how can I project my own self-importance today" and "which boy should I like?"
To be fair, she's about the best developed character in the series, but that's not saying very much. Her love interests are both bland dimwits, her mother should be an interesting character, but isn't; and the secondary characters in the alliance and her enemies are essentially cartoon characters. So, she ought to stand out since the book is told from her perspective, and her presence is there 24/7/365. But ... she doesn't.
Let me take just one specific: she's killed people. Those of us who have done that, or love people who have, would never believe in a character as apparently unaffected by it as she is.
Now as for the series: if you've read real fantasy and science fiction, this is simply NOT imaginative science fiction. It's at about the level of a Star Trek plot, which is to say: NOT ... IMAGINATIVE ... AT ... ALL. As for original, also, NO. It was done in Japan about ten years before The Hunger Games was written.
It's mildly pleasant, a quick read and not nearly as frequently cringe-producing as Twilight (a series I also worked my way through, with much more difficulty.)
Bottom Line: There are much better female characters in adult fantasy and science fiction, and those books are accessible to moderately intelligent kids, who would enjoy The Hunger Games a lot less if they knew what they were missing.