Retail stores like WalMart or Toys’R'us can sell your game, and it’s not impossible to get your game in sale through retail stores. There is a risk of getting ripped off (I personally haven’t dealt with retail stores, so I cannot give any personal recommendations in any direction) so that you actually don’t see any money after the first advance payment. I’m not saying that retail stores are out of question – just wanted to remind that they carry a risk.
Nevertheless, if you want to get your game to retail stores, I’ve compiled bunch of resources here. These companies can help you get your game to retail stores.
Big list of retailers:
List of companies / publishers that can help you to get your game to retailers (in alphabetical order):
Browse and see what could work for you. I’ve heard some good stories about Mumbo Jumbo and Meridian 4, but for further info – feel free to contact these publishers and ask yourself.