I live in the western Philly burbs. We used to have a Play n Trade but it closed a couple of years ago. It was pretty expensive from what I remember.
There are two decent retro game stores still in the area.
J Street games is in the King of Prussia mall, and I think they have a store in the city as well. They have a decent selection and fair prices, and they have stores in MA as well and are all connected, so if they have a game you're looking for at any of their locations they'll ship it to you.
There's
Classic Game Junkie in Glenside. The folks who run that store are nice, great selection and they even do console repairs. Prices are very fair, I've picked up a few gems there which would have cost me $20 more on Ebay.
And at the Quakertown Farmer's Market,
Video Bonanza. They get some good stock in but it's pretty broken in most of the time. Not really collector grade but good if you don't want to pay crazy prices for a near mint in box.
But the best thing about Philly is in a pinch I can run up to NYC and hit up
Video Games New York. That place makes me feel like I've died and gone to heaven.