The perfect game would be well written. Written in a way that anybody can pick it up and understand it. I understand what they were supposed to do, what the game was about, and what the rules and procedures were. It should be very clear about what you should do and shouldn’t do and what you should expect.
The perfect game would be well designed. It would have a particular genre or feel in mind and should communicate that. The system and mechanics should help reinforce producing that genre and feel. The game should explain that’s what they were designed to do And how they do it. The probabilities should be exposed so you can understand what it will be like. The game should be play tested.
All of that is very objective but what about my subjective requirements for the perfect game?
For me, the perfect game would have a somewhat narrow range of competency. Maybe that’s the wrong way to put it, but you should be able to create the sort of characters that you would like and that fit the genre. You shouldn’t have to create a character and then wait a long time to improve them to the point where they became what the game experience promised or demands.
The perfect game for me would be designed to facilitate an in character as character experience. The game master would have the responsibility of running the world, and the other players would be responsible for their characters and their decisions. That said, the perfect game would allow for player narration and description, especially when they were successful.
Finally, the perfect game would encourage interaction between all the players.
You’ll notice that none of this talked about what genre or what mechanics what system what probabilities… There are lots of perfect games out there. They are all different and they are supposed to be!