Exchanging games works by going to the "guest services desk" with the merchandise, it'll be scanned and, if the value is acceptable, the customer will receive a gift card. We're honestly shocked at Toys R Us accepting trade-ins that go all the way back to systems like the Atari 2600. We're following up for some more details and will update as soon as we hear back.
Update: Toys R Us is not getting into the used games resale business, it is merely accepting the used merchandise. A representative for the company tells us the games "are taken by a third party company that refurbishes them for resale." We're still following up to find out what company that would be. We'll update again when we find out.