Dear Alex,
You wrote that "sometimes" Ben will not let you pick the game. Does that mean that sometimes he does? If you pick the game half the time, and he picks the game half the time, that sounds fair to me. But if Ben is the one who usually picks the game you play, make sure he knows that you're not happy about it. He may not realize that he's been picking the game more of the time. And he may not know that you don't always like the game he chooses. If you let him know how you feel and he won't change, you might try playing at recess with some of the other kids.