The interesting thing about games is that there are so many different ways for a game to be enjoyable. Movies and books sort of have prescribed plot devices they need to follow. There are definitely experimental movies and books that achieve greatness, but experimental plot structures sometimes fall flat on their face with audiences. Case in point, with movies and books, audiences almost always need to connect with characters, and there aren't many avenues outside of that golden rule. With games, however, if I devised a rule, then I could probably come up with a hundred counter-examples of fantastic games that break the rule. You could devise a great plot with great characters, but you could also have a blank slate character (i.e. Mario) and it might be more advantageous to the game. Your characters might not feel like characters at all (i.e. a spaceship that shoots swarming aliens or a paddle that bounces a ball).
I am tempted to make some claims about difficulty curve, but some games kill you over and over but just draw you back. I suppose for audiences to enjoy your game at all, it shouldn't feel unfairly difficult. But then there are games (walking simulators) where difficulty isn't even a factor at all. For those reasons, I believe games are a medium that we haven't experienced before. I don't think we've even seen every genre of possible game yet.