Games have the potential to beat out all other mediums in terms of emotional impact, whether that emotion is sadness, anger, joy, intrigue or fun. Or anything else really. The fact that fun comes from play, and play generally means interacting with a set of mechanics and observing, predicting and manipulating the resulting change means that games most readily create the emotion of fun. Of course we need to define what "Fun" truly is. In a sense, picking apart the plot nuances of Schindlers List is fun, but the subject matter is too serious to comfortably use that word. Still, what you may call fun draws the observer into the work, and creates a more meaningful experience. Games are equally capable of doing this: Go play the game, "Passage", and tell me that you did not experience something profound, and I will call you a shallow soul indeed. Games should be fun, and every fun game that makes people enjoy themselves and have a good time is a blessing. But the fact that we by and large do not ALSO have more serious matters is a travesty that should be corrected.
Why are games more prone to be, "Just fun?" well, because doing more is a hell of a lot easier. Showing countless lives ruined by war in a movie is relatively easy: Just show the tragedy. This is an oversimplification sure, but there are very direct methods for portraying the horror of war. In games, and not just the non-game, cutscene bits added into games, this is a lot harder. You have to create a complex system of rules wherein the choices the player makes while trying to maximize the effectiveness of their strategy naturally lead to the conclusion that war is bad, and mistakes the player made that would lead to war are morally unacceptable. A movie can hit you over the head with a hammer, but a game has to make sure that a complex, massive series of choices naturally force the player to come to a conclusion desirable by the designers vision. The payoff however, is that when a Game gives you a message, you are not being told the message: Your actions make the player decide for themselves, of there own free will, that an artistic vision is true, and that you are the one who caused that vision to exist. Its harder to dismiss somethign that you yourself created in a very personal way. It's a lot easier to just make a complex system for the players to explore, and not worry about the ramifications. Hence, lots of fun games.
Why are games more prone to be, "Just fun?" well, because doing more is a hell of a lot easier. Showing countless lives ruined by war in a movie is relatively easy: Just show the tragedy. This is an oversimplification sure, but there are very direct methods for portraying the horror of war. In games, and not just the non-game, cutscene bits added into games, this is a lot harder. You have to create a complex system of rules wherein the choices the player makes while trying to maximize the effectiveness of their strategy naturally lead to the conclusion that war is bad, and mistakes the player made that would lead to war are morally unacceptable. A movie can hit you over the head with a hammer, but a game has to make sure that a complex, massive series of choices naturally force the player to come to a conclusion desirable by the designers vision. The payoff however, is that when a Game gives you a message, you are not being told the message: Your actions make the player decide for themselves, of there own free will, that an artistic vision is true, and that you are the one who caused that vision to exist. Its harder to dismiss somethign that you yourself created in a very personal way. It's a lot easier to just make a complex system for the players to explore, and not worry about the ramifications. Hence, lots of fun games.
D was fun, but when you try to explain the game, it's hard to see how that would be fun to someone who has never played a second of the game. Or even Super Meat Boy, one of the most frustrating games out there is still fun and still interests you in its great art design, humorous style and solid controls. 
