What makes Ender's Game so tense and riveting is the brutality and honesty of the children, especially the lead character. It is lord of the flies with a sci-fi backdrop. No one in the book is more brutal and sociopathic than Ender himself (except maybe for Peter who is not a real character anyway). Unfortunately I think the movie version will play up the sci fi elements and go for a Harry Potter meets The Last Starfighter vibe, which would be painful to watch and another waste of a potentially interesting property.
Card's books after that were all failures in my eyes, his first set of sequels sought to atone for the brutality of the first book.The second set was a cash grab from an author desperate to rescue a dying career. Only the bean one was even readable and all that does is retell the original story through a character that is a more extreme representation of the original.