This app was mentioned in 5 comments, with an average of 1.80 upvotes
If you've got an android device, you can try Biz Builder Deluxe One of the kinds of shop you can open is a game shop, and the game itself is rather fun.
Not free, but several Kairosoft games are like this. The newest (and most varied) being Biz Builder Delux.
Linkme: biz builder delux
[EDIT] Well, the linkbot got it very wrong. Here's the proper link.
Recettear is great fun, and I second everyone's vote for it.
If you have an Android device, I also recommend Biz Builder Delux (https://play.google.com/store/apps/details?id=net.kairosoft.android.townshop_en) - it's not like most mobile game crap where you're waiting time to do anything. It's an actual pay-for game, fully unlocked, that you play at your own pace. You can run up to three different stores at once, of various products, either stocking or producing them too. Quite fun!