Hmm Carrefour is conquering the world, second biggest retailer in the world after Walmart. They are all over here in France, started on a discount model and later beefed up prices when all the smaller retailers were either dead or acquired.
I hate them but they are a good place to shop in China, there are over 100 there now. For those looking in Shenzhen, there is one right off the Gangxia metro exit.
From my experience, facial cream for ladies are the absolute killer, I got requests for Body Shop and Nivea products ... which you can find in China as well if you look, there's a Body Shop store in a shopping center in Shenzhen/Shekou, even European chocolates are omnipresent in stores (at least in Shenzhen), it will be harder and harder to bring something really unique and inexpensive.
From France I would bring wine/champagne as Chinese prices are sky high and the selection is still limited. Some local food specialities like foie gras could work, and of course Belgian chocolate, but not the one in bars mind you, rather a box of Leonidas ...