The main thing a game should be is fun and fair. After all, what's the point of playing a game that isn't enjoyable! If a game isn't fair it can create a hostile environment and tarnish the representation of it and if one person has a considerable advantage given to them then the chances are that it is not fun. Also, goals are a very big portion of why people play games in the first place, when you finish a level or achieve a certain rank you are supposed to feel good and accomplished, and if a game has a long-term goal it can make the game have increased replayablility and on people can play more on a regular basis.