Create a flag for games to be "greatest hits/player's choice" versions, or create different listings than the "black label" original printing of the game.

Greatest hits versions look hugely different than the original printing (also called "black label") of the game.  They look different, they're less desirable to collectors, and therefore are usually cheaper than the black label version of the game.  

Not including the ability to differentiate greatest hits/player's choice from the black label editions of a game also distorts average price since the cheaper greatest hits sales lower the averages of the black label games.