Personalized game recommendation to edit
As means of promoting game editing, there could be a game recommendation for the user. It would be based on the game pages the user visited, the games the user rated, etc. A notification could appear on the website with the recommendation, and there could be a place in "Karma hunters" for some more recommendations.
It would certainly help with many more game info missing, as the person would be prompted to help with something they most probably know.