As there are sometimes games created who already are on the site, it may be a good idea to add some kind of warning line in the beginning of the game creation module, like 'Please check if the game you want to create already exists. You may use the search tags to check'. That's all :)
Just a suggestion.

I agree there should be such a warning line. But if there exist two similar games, sometimes the second one is better or has some other tings in it, too. I think in every known case there should be a link from one game to the other so the player can have a look at both of them and decide for himself. It should be in the comments of an old game, too, if a new game picked up the same idea. Often you don't know there are similar games, that's a pity because you might like to play them all. If you played both you should write in the comment's of both what's you opinion which game is better or what you do like better in one and what in the other.