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, you can find these opportunities 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 focus 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:

  • General Electric (NYSE: GE)
  • Patriot Coal (NYSE: PCX)
  • Perfect World (Nasdaq: PWRD)
  • Dean Foods (NYSE: DF)
  • Yamana Gold (NYSE: AUY)

Some of these names might surprise you. For example, superconglomerate General Electric has been an industry leader in consumer goods, health care, and now alternative energy. Almost great? Even familiar names can still offer some of the best opportunities. Perhaps we've just forgotten the potential they still hold.

The recent explosion at Massey Energy's (NYSE: MEE) West Virginia coal mine underscores just how dangerous a job mining is. However, coal remains one of the energy resources available in the U.S. that can help us break our dependence on foreign fossil fuels. Patriot Coal will be one of the miners capitalizing on that.

Still, the 165,000-plus CAPS members chose these companies as less obvious sources for tomorrow's great buys. Let's see why they might merit your attention.

In the sight of greatness?
Chinese online gaming specialist Perfect World's latest earnings report showed the world it wasn't perfect. The ranks of its active paying customers diminished by 500,000, shrinking to 1.7 million. Yet the company nonetheless increased average revenue per user by 37%, helping it generate total revenues that grew 47% to $91.6 million.

Internet gaming is becoming a crowded, competitive space, and not everyone is able to extract even Perfect World's meager gains. Shanda Games hasn't been an investor favorite ever since its spinoff, and is finding limits to its growth amid stiff rivalries and government regulation.

CAPS member armyofmeat says that although Perfect World could probably use a refreshed lineup of games, the fact that the market is still growing, albeit more slowly, means that the company will garner its fair share of gains:

This is a growing market, and even though their current cash cows are a little long-in-the-tooth, their past releases have shown strong enough acceptance by the Chinese gaming market, that we can assume their future releases will carry the same goodwill for at least the immediate future 

On the shoulders of giants
Analysts were milking Dean Foods' earnings report for all it was worth, downgrading the stock after the dairy processor had to yank its full-year guidance. With price competition in its private-label milk business pulling profits down 43% from a year ago, Dean will be thinning its herd, cutting hundreds of employees in an attempt to control costs.

With more than three-quarters of its revenue coming from the dairy sector in 2009, it's smart for Dean to try and become a lower-cost provider. Wal-Mart Stores is its biggest customer, accounting for about 19% of sales last year. The Bentonville Behemoth is notorious for squeezing its suppliers, particularly now that it has resurrected its "rollback" advertising gambit to lure in more customers.

Writing earlier this month, CAPS member TheStock says there's no reason to cry over spilled milk:

This is a cash cow stock (actually a milk cow stock, sorry for the geekiness) that has a P/B ratio of 1.3, a P/E forward ratio of 6, and has manageable cash and debt levels. The core business is profitable. The stripped rating that led to its rapid decline in price this month is based on tightening margins due to increased expenses. Management has talked about cutting costs in the short term and so the long term prospects for this stock look good as I see it trading at a big discount to intrinsic value.

A big opportunity
First Greece collapsed. Now Spain's shaky, as the dominoes in Europe appear to be lining up for a cascading fall. Gold is already trading at record levels because of financial jitters in global markets, and any additional signs of crumbling support will cause it to bound higher.

At just 15 times 2011's earnings, Yamana Gold is cheaper than many others in its industry. Goldcorp (NYSE: GG) trades at 25 times earnings, and Royal Gold goes for north of 36 times next year's profits. With the potential for higher prices in the near future, CAPS member Grinder63 considers Yamana undervalued:

Holder of several large properties in mostly politicly stable countries. With gold set to take off short to mid term, this undervalued stock is set too outperform. [Yamana Gold] is also an [excellent] aquisition target for a larger corp.

A great opportunity for you
Investor sentiment suggests that these four-star investments still seem to be on their way to five-star greatness. Nonetheless, 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.

Wal-Mart is a Motley Fool Inside Value pick. Perfect World is a Rule Breakers recommendation.

Fool contributor Rich Duprey does not have a financial position in any of the stocks mentioned in this article. You can see his holdings here. The Motley Fool has a gold-plated disclosure policy.