My suggestion for the checkmark: make it different icons depending on play-state:
unplayed (hasn't been played yet)
being played (has been played)
waiting for update (the user set this flag to indicate he finished the game in its current version, but the game isn't complete yet)
finished (game has been played through and is completed)
unplayed (hasn't been played yet)
being played (has been played)
waiting for update (the user set this flag to indicate he finished the game in its current version, but the game isn't complete yet)
finished (game has been played through and is completed)