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 5,300 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 companies approaching greatness. Here are just a handful:

  • Arena Pharmaceuticals (NASDAQ:ARNA)
  • Century Aluminum (NASDAQ:CENX)
  • General Electric (NYSE:GE)
  • Intel (NASDAQ:INTC)
  • Stone Energy (NYSE:SGY)

Some of these names might surprise you. Super-conglomerate General Electric has been an industry leader for more than 100 years. Almost great? Even familiar names can still offer some of the best opportunities. Perhaps we've just forgotten the potential they still hold. However, the 140,000-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?
The same economic gyrations crimping Alcoa (NYSE:AA) are also toying with Century Aluminum. Even with demand increasing, aluminum producers must work through a huge amount of inventory before prices can recover. London Metal Exchange figures show that aluminum supplies fell by more than 4,800 tonnes, but remained near record territory of 4.6 million tonnes. China is also experiencing an oversupply situation; Aluminum Corp. of China (NYSE:ACH) figures it could take as long as three years to resolve.

Although aluminum prices have bounced well off their lows, they also remain well below the highs they achieved last year. Earlier this year, CAPS member mccarthyconsultg argued that record low pricing created a tantalizingly shiny opportunity:

Enough blood has been shed in the global bauxite, alumina and aluminum sectors. CENX has experienced a dramatic decline in its value over the past 2 years. In my opinion, CENX has now hit its bottom (or very close to it). It may move laterally for a while, and rebound with other industries operating in the basic industrial sectors of the economy. One important competitor of CENX operating in Central America (Jamaica) has closed its operations and may not reopen for another 12 to 18 months. The Central American closure will reduce the supply of alumina on the global market and should contribute to an increase in demand for CENX's products.

After soaring from those depths, though, how much further can Century Aluminum run? This summer, CAPS member pradsynair predicted that the company's cost-cutting measures were a shrewd move. Century Aluminum has gone even further now, selling its stake in alumina and bauxite joint ventures to focus on its core aluminum smelting activities. For CAPS member Hogty, it's only a matter of time now before pricing corrects itself.

Fat Tuesday
... and Monday, Thursday, Saturday, and every other day of the week ending in y. According to the Centers for Disease Control, Americans live in a "obesogenic" society, an environment that encourages excess food intake while living a sedentary lifestyle. That might not do much for our waistlines, but it ought to do a lot for Arena Pharmaceuticals. The company's gearing up for phase 3 clinical data for its anti-obesity drug Lorcaserin, which is slated for release sometime this month.

Highly rated CAPS All-Star clawmann says the likelihood that the data from Lorcaserin's BLOOM trial several months ago will be confirmed by the clinical trials, and its high safety profile, both make it a good prospect for FDA approval.

Analysts are encouraged, too, expecting that doctors will want to prescribe a drug that has a high chance of helping patients reduce at least 5% of their body fat without serious side effects. Lorcaserin might not be as effective as some other drugs, but "not killing the patient" is always a key consideration. Phen-fen was effective, but the fatal increases in blood pressure it triggered led to lawsuits, and it was swiftly pulled from the market. If Lorcaserin's data reports as expected, and FDA approval comes within a reasonable amount of time, look for Arena to partner up to market it sometime next year.

President Obama will be giving a major speech on Wednesday to boost his health-care reform package. Whatever side of the debate you fall on, LimoDriver1971 argues that obesity drug companies like Arena will benefit from a systemic overhaul.

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

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