There is a "mall" at Bay and Dundas underground called Atrium on Bay you will see a liquor store and a black photo shop. Or better yet near Spring rolls. It has access via the South train. And right beside the down escalators there is a used games/movie store there. I always see alot of people so i think it's worth a shot.
Best place I would say is EB(Electronic Boutique) inside the Eaton Centre(Sears Centre) They have good prices on new and used games. They have a membership as well where you get 10% of every purchase.
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