I think a good game design should take into consideration a growth and reward system. There should be stages the protagonist goes through, and after these stages, if they are completed within satisfactory parameters, the protagonist will grow. Eventually, this growth will reach a stage where the character can obtain the reward. Most early games have simple growth and reward systems. For example, in asteroids, the growth would be to destroy all the asteroids. The reward would be the next stage with more asteroids. But if you apply it into current generation games, the same concepts apply. The more intricate the growth stages are, and the more rewarding the rewards are, the better the game. Most RPG (Role Playing Games) were spawned from this concept. For example, to grow you would defeat enemies to obtain experience and gold. The rewards was that you can use the experience to gain more powers (magic or strength, or somethings similar for better spells and hit damage), or better equipment (buy better armor or weapons at the stores for example).
But what most game designers forgot along the way was making the growth stage and the reward stage climatic. The rewards should be layered such that you don't actually know the whole reward is, but are hinted at it. And the growth stage should have mini-arcs of climatic improvements. This way the player feels the improvement. But if you improve without opening up new rewards, the game gets boring. And if you know right away what all the rewards are, it also gets boring (you don't want them to know the ending of a good book before it is time).
One of the hardest things a good game designer should take into account is the growth stage. It has to be fine-tuned so that it is fun, not too hard, and not too easy. It must be uniquely refreshing to play. This is why most games should take some concepts from the movie industry. In movies, if you know the ending then it is not worth watching. Similarly, if there is no climax in the film, it is also boring. The movie usually have some sort of hook to drag you into the show. So if you were to take this into the gaming world, the game should have endings that are not predictable... things you can't guess at in the beginning. As you grow into the game, going through the mini-arcs, you grow and gain new knowledge or abilities, which help unlock the rewards. As an example, suppose in the beginning of the game there is a cave that you can't enter, and people say strange things are in the cave. You would not be able to enter the cave until you have mastered or achieved via growth by playing the game. After you enter the cave, more intriguing things may be found, thus following the concept of a good growth and rewards system.
If you think through this concept you will find that most good games have good growth and reward systems. Whether it be getting the highest score, defeating all the enemies or bosses, or simply following through the story. Usually you can unlock things. However, most games these days are forgetting to put in the fun factor into the growth stage, and leaving the reward too weak. In many games the climax and ending is known before you even start the game. You should be unlocking mysterious things that open up new realms and rewards, not stupid stuff that offer no real change in gameplay.
So the next challenge of the next gaming revolution would be to see who is able to create games that hooks you into it, allow you to grow indefinitely in it with layered rewards. The layered rewards are challenging in itself, which may take too long to write in this short piece.
