Wal-Mart (NYSE: WMT) is still the king of the retail jungle, but its relative dominance seems to be slipping. At least that's what a recent survey of 30,000 shoppers from Consumer Reports suggests.

As the voice of smart shoppers, Consumer Reports discovered that among popular chain stores Wal-Mart was bested by Costco (Nasdaq: COST), which scored top marks in the recent study. In fact, Costco was the only store among the 11 featured in the study that was judged "much better than average for value."

According to Consumer Reports:

Wal-Mart was the sole chain to receive below-average quality scores in more than half of the product categories. ..

For all the talk about Wal-Mart's low prices, shoppers said the prices at 10 other retailers, including JCPenney [(NYSE: JCP)], Sears [(Nasdaq: SHLD)], Dillard's [(NYSE: DDS)], and Meijer, were at least as good. And bigger wasn't necessarily better when it came to the overall shopping experience. Almost three quarters of respondents who shopped at Wal-Mart found at least one problem to complain about, and half had two or more complaints about the store or its staff.

Strikingly, Wal-Mart did not have the mindshare as the low-price leader, which may be reflected in the company's inability to boost same-store sales in the last four quarters. And dollar stores are increasingly creeping into Wal-Mart's grocery turf. But in recent weeks, the company has gone on the offensive, pruning prices on thousands of items.

While some shoppers are turning to the more chic Target (NYSE: TGT) as their incomes improve, the survey indicates that the retailer's women's clothing and jewelry were ranked below average.

If prices are all that matter, and the Consumer Reports survey is correct that Wal-Mart is no longer the low-cost leader, are shoppers ready to dethrone the retail king?

Jim Royal, Ph.D., does not own shares of any company mentioned in this article. Costco and Wal-Mart are Motley Fool Inside Value recommendations. Costco is a Stock Advisor pick. The Fool owns shares of Costco. Try any of our Foolish newsletters today, free for 30 days. The Fool has a disclosure policy.