There are perfect games. Why? Well humans don't know what perfect is anyways. Perfection is something that is beyond human knowledge. That's why we call something perfect. It's the incomprehension of something that is perfection.
Thus perfect has been adapted to critics to be more well known as the best in the certain industry. Meaning things can have a few minor flaws, but if it excels over everything before it and makes leaps and bounds in numerous areas, then we have perfections.
But in normal terms, perfection is simply the incomprehension of something or over our heads. Thus it must be perfect. Kinda an arrogant thing man uses as well but whatever.