The lights are on
What new ideas the game brings to the table and how well old ideas are presented.
How good a game looks, taking into account any flaws such as bad collision or pop-up.
Does the game’s music and sound effects get you involved or do they make you resolve to always play with the volume down?
Basically, the controller to human interface. The less you think about the hunk of plastic in your hands, the better the playability.
Flat out, just how fun the game is to play. The most important factor in rating a game.