I don't normally do these types of posts but I figured why not? This is just a personal comparison. Please note that I am ONLY comparing the movies as I have not read Battle Royale in either it's manga or novel form. I have only read the Hunger Games books. This is my personal view/opinion on the two movies. If you disagree that's fine. Everyone is entitled to their own opinion and view. I am not here to fight over this so please do not start an argument on my post.
I finally sat down and watched Battle Royale today. People have been comparing Hunger Games to that (mostly those who hate HG.) So I watched it with an open mind.
The main thing I found alike was that it was a bunch of kids killing each other and the government was involved in some way. In BR they straight up said it was punishment, in HG they said it was to help people "remember" what they did wrong. The back story for HG was more detailed or at least it was described in more detail. I may have to go back and watch BR again just to see if I missed anything. Subtitled movies are always harder to watch because you really have to pay attention. If you look away for even a moment you may miss something vital.
In BR it was a randomly selected class of school kids. (The entire class.) They also have no clue what is going on until they get there. In HG it was two kids randomly selected from each "district". Which would kind of be like each city in a way. The kids in HG know it's coming.
In BR there were more than two people who got out in the end.
In BR they were on an island where as in HG they were in places that were man made or specifically set up for them. In HG one girl starts the revolution and all the cities join in. In BR it's just a group of students who do it.
There were a few other similarities and differences but it would take me longer than I have to list them all right now.
I actually enjoyed both movies but I have to say I liked HG more for many reasons. As I said above the story was more detailed. Also I felt I could relate to the characters from Hunger Games more. This could be in part due to the fact that I only read the Hunger Games and I'm sure the language barrier was contributing factor also.
I guess in summary while there were some similarities in the two stories I feel they were also both unique in their own way. So I don't think it was necessarily a "copycat" thing. The author of HG may have been influenced by it, but most authors are influenced by other authors/stories in some way. Even if they don't realize it at the time. Then again the whole idea of a government controlling and abusing society and people uprising was not invented by BR. That story has actually been around (and used) for a long time. So really the few similarities could also just be a coincidence.