He, the perfect game? That's something hard to explain...
It depends of the kind of game you're playing. But for me, the main thing is: It has to be TESTING me, it has to be some kind of challenge, and it has to entertain me for some reason.
What make Tetris, Pacman , Rally-X or Tempest nice to play? They don't have much variation, but they are fun because you are always thinking fast, reacting fast, changing your strategy "on the fly", adaptating yourself to the situations in the game, situations that change at every second.
But you also have lemmings, chip's challenge, games where you can stop, take a deep breath, and think about the solution. You have to THINK, and that's something that have been entertaining people for ages (Why someone would enjoy doing cross-words?)
In games like Frontier or Elite, you can feel like you are living something else, something that could only exist in fantasy books, and you are free to do whatever you want in this new world. You can be a criminal, or you can be a federation soldier. You can break up from the problems of the real world, and just enjoy being something else for a while.
In R-Type, Battle Squadron , Xenon 2 or Apidya, you don't want to think, you don't want to believe you are in another world, all you want to do is blast some stuff, and dodge some bullets. Yeah, you just shout "shoot me", and dodge everything. You turn off your brain and let your reflexes talk by yourself. You test your skill at the maximum.
You have games like Monkey Island or Beneath a Steel Sky, where you have a great story running, and you can interact with the story.. you are PART of the story, it's just like being inside a movie.
Damn, I could be writing stuff like that for hours, and still I couldn't get to the point of what makes a good game. There are so many things that makes a game good. Does it need to be original, simple, complex. long, short, or anything? No, it doesn't. If you try to mix all this together, you probably won't get a good game (Actually, I think you would get a perfect $$$ money.. just look at the ads: The originality of X game, the gfx of Y game...). The only thing a game need to be good is to be FUN to play. And I mean REALLY fun, the kind of fun that makes you forget for a few minutes that there's a world outside of you, it makes you shout at your computer while playing it, it makes you celebrate when you win, it makes you laugh at the computer when you do a good move, it makes you shake while you play it, and when all is over, it makes you feel like the game is like a friend of yours.
He.. and I scored 0% in the geek test ,huh?