Among other things, Collins seems interested in mounting a critique of a society much like our own, a society that hungers for the dangers of "reality," but only as observed from a safe distance; i.e., while watching television. It's also important to know that in The Hunger Games, the children do not kill for kicks or because they are inherently evil. They kill because they're forced into a situation in which they have no choice. Each participant in the games is selected by lot and thrust into a lethal game that allows for only one winner.
Kids are also human, so it's hardly surprising that some are buoyed by the attention they receive prior to the games, that some form self-serving killing alliances during the games and that some are more eager participants than others. By the story's end, though, Collins introduces an act of resistance that can't be written about in more detail without introducing spoilers, but which should be taken into account when evaluating the movie.
There are no inviolable rules when it comes to criticism, but rejecting a work because of its subject usually makes little sense. It's not necessarily a film's subject that matters, but how a filmmaker deals with that subject. Whether The Hunger Games succeeds or not can be debated, but -- in my view -- neither the movie nor the book qualifies as exploitation.
Apart from all of this, it's not my business to tell people why they should or should not see a movie, but to think and write about whether a movie succeeds or fails -- or does a bit of both. It's up to readers to decide for themselves whether they're interested enough to see the work in question or prefer to stay home.
And if you're looking for a guideline about the age at which The Hunger Games becomes appropriate viewing for young people, you can note the movie's PG-13 rating. An even better guide may come from the book itself: Katniss -- the young woman we follow throughout the book and movie -- is 16.