For a while now, investors have wondered whether Wal-Mart (NYSE: WMT) could successfully jump-start U.S. sales. Alas, fourth-quarter results reveal that it still can't. The Bentonville Behemoth lumbered its way through a woefully disappointing holiday shopping season.

Wal-Mart's fourth-quarter income increased 4.3% to $5 billion, or $1.41 per share. Revenue increased 2.5%, to $115.6 billion. To understand why critics have begun to question the retailer's current strength, take a gander at Wal-Mart's same-store sales figures. Here in the U.S., Wal-Mart's comps fell 1.1% (or a 0.8% decline if you factor in fuel sales).

The discount giant attributed the U.S. comps decline to a slowdown in customer traffic, since average ticket rose a tad from the same period last year. Still, the timing of the fourth-quarter results suggests that Wal-Mart failed to win robust customer interest during the crucial holiday season, even though it was a huge contender in the battle to lure customers with aggressive come-ons.

Offering free shipping and other dubious deals didn't save Wal-Mart's holidays. Plenty of retailers like Best Buy (NYSE: BBY) touted similar deals, and the exclusion of hot products like Apple's iPads from Wal-Mart's deal made that offer look a lot less enticing.

This is the seventh consecutive decline in the retailer's quarterly same-store sales figure. That doesn't bode well for Wal-Mart, and definitely makes rivals like Costco (Nasdaq: COST) look far more promising at the moment.

In this difficult economic climate, Wal-Mart's core customers are feeling budgetary restrictions. Luring more affluent customers from the likes of Target (NYSE: TGT) and Costco is easier said than done. And on the less affluent end, Wal-Mart needs to contend with super-deep price cutters such as Family Dollar (NYSE: FDO) and Dollar General (NYSE: DG).

Wal-Mart's desperation to do something about its flagging sales even drove the company to increase some of its prices last year. After building its reputation on rock-bottom prices, Wal-Mart's playing a dangerous game when it makes such moves.

Even though its stock trades at just 13 times earnings, far cheaper than the multiples attached to stocks like Costco, Family Dollar, and Dollar General, Wal-Mart's current growth obstacles make the stock sound anything but worry-free at the moment.

Share your thoughts on Wal-Mart's future in the comments box below, or add it to our My Watchlist feature to keep an eye on its progress.  

Best Buy, Costco, and Wal-Mart are Motley Fool Inside Value picks. Apple, Best Buy, and Costco are Motley Fool Stock Advisor recommendations. Wal-Mart is a Motley Fool Global Gains selection. The Fool has written puts on Apple. The Fool owns shares of Apple, Best Buy, Costco Wholesale, and Wal-Mart. Try any of our Foolish newsletter services free for 30 days.

Alyce Lomax does not own shares of any of the companies mentioned. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.