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
The data shows that stocks achieving five-star ratings on Motley Fool CAPS have outperformed the market by 12 percentage points, and newly minted five-star stocks represent your best opportunity to capture those returns. So let's sift through the proprietary ratings system and find those stocks heading toward superstardom. Here are a handful of four-star firms approaching greatness.

  • Alcoa (NYSE:AA)
  • Arena Pharmaceuticals (NASDAQ:ARNA)
  • Broadcom (NASDAQ:BRCM)
  • Massey Energy (NYSE:MEE)

Some of these names might surprise you. International Business Machines has been synonymous with top business practices for decades. 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 120,000-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
Great investors like Buffett and Lynch often look for companies whose stocks have been beaten down for reasons completely unrelated to the business. Having a solid business despite great turmoil around you is a mark of a top-flight company. CAPS member Foliobuilder thinks he's found a similar situation in aluminum producer Alcoa:

Alcoa is not a financial institution with CDOs and credit default swaps lurking on the balance sheet. It is a manufacturing company with few direct competitors. (Yahoo finance considers steel companies to be its competitors). Industrials will again be in favor if this country hopes to pull itself out of economic calamity. Aloca will be a part of this transition once the US changes it focus to becoming a manufacturing nation again.

A number of semiconductor companies see a future of pain. But Broadcom is looking to new technologies as a means of maintaining -- if not expanding -- market share. One such opportunity is in providing a chip for LG Electronics that combines Blu-ray access with the ability to stream movies via Netflix (NASDAQ:NFLX) downloads. CAPS member chaaya1 blames Broadcom's suffering on the weakness of its rivals rather than on any problems of its own design:

A provider of semiconductors & integrated circuits. Hit hard by the general down turn and weakness in the semiconductor industry and its ongoing duel with other players (ex: QCOM). Will eventually come out of its current rut and settle or win many of the current disputes and when it does, it will be a 2 to 3 bagger in 2-3 years

Maybe we should call it a fat opportunity: Arena Pharmaceuticals' obesity therapy holds definite promise, and with sufficient cash in the coffers, it should have enough to weather the current credit storm. According to one analyst, while profitable biotechs like Amgen (NASDAQ:AMGN) are in no danger, there are only a handful that have more than a year's worth of cash on hand. With the company expecting to end the year with $115 million in the bank, Arena falls in the "safe" category so far -- even though it started the year with almost $400 million in cash and investments. Still, we've been aware of that cash burn for a while.

CAPS member prosper21sees the lorcaserin drug as the catalyst that pushes Arena higher:

December Phase II result of APD 125, combined with March 2009, First Phase III Lorcaserin Result, and September 2009, Second Phase III Lorcaserin Result, NDA by end of 2009 for Lorcaserin, is a great catalyst for Arena Pharmaceuticals, Inc.

A great opportunity for you
These four-star investments are on their way to five-star greatness, and 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 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 disclosure policy.