Some companies are obviously great investments -- in hindsight. Yet for every stock out there screaming "buy me," others simply give us a nudge and a nod. How can we tell tomorrow's obviously great investments from the thousands of pretenders?

The stars' walk of fame
On Motley Fool CAPS, these opportunities can be found among our four-star stocks. In CAPS' proprietary ratings system, they rank higher than most of the other 5,400 starred companies, but they're just shy of superstardom. While all the attention might be focused on their five-star peers, we can sift through CAPS to find four-star firms approaching greatness. Here are a handful of four-star firms approaching greatness.

  • Duoyuan Global Water (NYSE: DGW)
  • K-Sea Transportation Partners (NYSE: KSP)
  • Pain Therapeutics (Nasdaq: PTIE)
  • Puda Coal (Nasdaq: PUDA)
  • Skechers (NYSE: SKX)

Some of these names might surprise you. Marine transportation firm K-Sea Transportation Partners, for example, was able to surprise the market by reporting significantly better than expected results due to the oil spill cleanup going on in the Gulf of Mexico. Almost great? Even familiar names can still offer some of the best opportunities. Perhaps we've just forgotten the potential they still hold.

And Puda Coal has been rising quickly in the estimation of the CAPS community. It was the end of September that the Chinese supplier of high-grade metallurgical coking coal to the country's industrial base was identified as a company ready to take off. Its shares up some 30% since then. However, the 170,000-plus CAPS members chose these companies as less obvious sources for tomorrow's great buys so let's see why they might merit your attention.

In the sight of greatness?
Wastewater treatment is a rising concern in China as economic growth and a burgeoning middle class make clean water issues a top priority. Treatment specialists like RINO International (Nasdaq: RINO) have enjoyed the benefits of greater attention being placed on the sector, and while Duoyuan Global Water was a partner in the rise, the bogeyman of small cap Chinese stocks these days -- financial and governance issues -- have sapped its strength.

In September a Duoyuan affiliate, Duoyuan Printing, fired its accountant and both its CEO and CFO resigned from their respective positions. The chairman of the company's audit committee also resigned along with three other members of the board. Fearing the contagion would spread to the wastewater treatment company, investors scattered and the stock dropped almost 42% in just one day.

Obviously there's going to be a lot of uncertainty until the matter is cleared up, but highly rated All-Star CAPS member DarthMaul09 is optimistic based upon the company's willingness to launch a preemptive, third-party audit.

Encouraging news that the company's management is teachable, in that it learned that if you lack all credibility your stock will lose all value. By willing to undergo a third party audit, it will likely find that its finances were not as good as reported but also that the sell off overshot the true value of the company. Even if it splits the difference and comes back to $16, that would be a nice gain from here.

On the shoulders of giants
(NYSE: PFE) made the royal decision to pad its pain medication portfolio by buying King Pharmaceuticals, which has been working with both Acura Pharmaceuticals and Pain Therapeutics to bring alternatives to oxycodone to market. Pain Therapeutics drug is thought to have a better shot at approval because it is a long-acting version with tamper-resistant features.

Now with Pfizer potentially backing the effort, investors are looking for PT to capitalize on the situation beyond what a short squeeze would give them, as LifeForceDance suggests.

You can weigh in yourself on the Pain Therapeutics CAPS page and add the stock to your My Watchlist to get all the Foolish news and analysis aggregated for you.

A big opportunity
Shoemaker Skechers says it owns 55% of the "toning shoe" market, but when that niche is little more than a fad, it doesn't amount to much. It's hard to come to any other conclusion when the company reported inventories were piling up and retailers were cancelling orders. Heely's investors laugh at how fast the fad dissipated.

For its part Skechers is laying the blame at a seasonally weak back-to-school period and says it still wants to unload the excess inventory at a "decent margin." But with every shoe company from Jones Apparel to Payless Shoes introducing their own line (even Crocs is getting into the act), the premium Skechers has been selling the shoes for simply can't stand.

With 94% of the nearly 500 CAPS members rating Skechers to outperform the market, it seems clear they think the stock has a good chance of regaining its footing. Head over to the Skechers CAPS page and let us know if you think this sneaker maker can kick it into high gear.

A great opportunity for you
Investor sentiment suggests these four-star investments still seem to be on their way to five-star greatness, but it pays to start your own research on these stocks on Motley Fool CAPS. Read a company's financial reports, scrutinize key data and charts, and examine the comments your fellow investors have made all from a stock's CAPS page.

Sign up today for the completely free service and let us hear what you have to say about the great and almost great companies that interest you.