I vote on Wal-mart as one of the worst video game retailers because although they do have low prices in the store, however that can't be said with the games because I see that everything is cornering the games as a prisoner, which isn't a good sign.
As for the best video game retailer, it has to be Best Buy because of their reward system and the easy transaction of purchasing gift cards/gaming cards.
On a side note, I will update this later on for more on my thoughts and reasons why for my choices.