Do not read this post if you have not seen the movie or read the book, and intend to do so, it will spoil it. :(
I read the book when I was a kid, and still remember the ending when they told him the battles were not a simulation. I thought the movie was a good representation of the book, though there were some differences. Before I went to see the show I was wondering If they were going to include the computer game that he could never win, It was nice to see that they did. They did a good job showing ender's "mama bear" combination of violent and emphatic traits, but it was only mentioned once that he was a "third". In the book he was ridiculed for being a "third" quite often.
In the book version (if memory serves correctly) the kids gave orders to the crew of the spacecraft more face to face on video communication, and in the movie they did not show any person on board the spaceships receiving the orders. It was only in mention at the end that they were crewed by real people. The book version had them using different spacecraft in all the battles, not the same ones like in the movie. The last battle in the book for example had the oldest and least technologically advanced ships, because they were the farthest from earth. The "simulations" in the book were all part of the "real" campaign, but in the movie I had the sense that only the last battle was "real" and the previous ones were "simulations".
It was not confirmed in the movie that he killed the bully, which in the book he did, and was an important part of the story. Killing the bully was one of his "tests" in the book, and he passed. Ender was created, through manipulation, lies and deceit, to do what he did. I guess the same could be said for a lot of us humans here on the planet now.