The competition is divided into various categories, and you will be marked appropriately by the judges. You will be judged on five factors, and a comment will be left underneath the final score by each respective judge.
GRAPHICS /20 - How well detailed are they? Does everything match the theme?
SOUND /20 - How the music chosen is suitable enough for Christmas
GAMEPLAY /30 - How fun the game is
PROGRAMMING /20 - How well programmed the game is... are there any bugs?
CHRISTMASSINESS /10 - How Christmassy is it? Does it tug the heartstrings of Christmas fanboys?
It's worth noting that you should try and aim to excel in all areas. The more effort you put in, the more effort you put out. That said though, you don't have to create super detailed sprites or the world's most perfect engine. Consistency, and ensuring the game is fun to play, are probably the two most important factors. But that doesn't mean you should be lazy with the other categories either!
The maximum score your game can get, by each judge, is 100 points. Your game will be ranked on the judges combined score, however, and this will determine your position in the final standings. Should there be a tie between the top two games, an angry debate will probably rage in the admin forums until a winner has been decided ;)