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 firms approaching greatness. Here are a handful of four-star firms approaching greatness.

  • E*TRADE Financial (NASDAQ:ETFC)
  • Freeport-McMoRan (NYSE:FCX)
  • ReneSola (NYSE:SOL)
  • Sequenom (NASDAQ:SQNM)
  • Yamana Gold (NYSE:AUY)

Some of these names might surprise you. Discount broker E*TRADE Financial has been an industry leader since the start of the financial services revolution. 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?
There's little doubt that if Sequenom is to become the company its investors think it is, getting its SEQureDx test for Down's syndrome right is a top priority. The company has been operating with a cloud of doom hanging over it since the fiasco with SEQureDx's clinical data came to light earlier this year. With an addressable market of around $1 billion, it needs those results verified; the sooner, the better.

While the news that it launched a cystic fibrosis test boosted Sequenom's share price, it's understandable that it all appeared a bit underwhelming. A market potential of just $300 million doesn't seem all that exciting in comparison.

Still, let's not dismiss this and other tests out of hand. Even if the SEQureDx results are validated, the additional revenue streams the other tests produce will provide the biotech with a nice source of income above and beyond SEQureDx. Getting enough of them to market will help diversify the company's sales, and keep it from being just a one-hit wonder. Moreover, these additional tests will help expand the market for its MASSarray technology, which is suffering a sharp drop in sales this year.

For example, MASSarray tests discovered that as many as 15% of women tested via other means for cervical HPV, and found to be negative, may actually be infected at relevant levels. In that light, highly rated CAPS All-Star Fuma102 thinks that focusing just on the Down's syndrome test is a mistake:

Their science is sound, despite questions about their trisomy screen. Don't take my word for it, take the word of the 170 other papers published based off their platform. No questions on their HPV screen, though. Which, btw, is more accurate & more specific with fewer false negatives & fewer false positives than current standard of care. a 3.6B market. yeah, no one talks about that. Too scared about that trisomy data still? You can all be scared, this is a 5 bagger in 2 years, even if one of these fails.

With Exact Sciences (NASDAQ:EXAS), Life Technologies (NASDAQ:LIFE), and others developing diagnostic tests of their own, Sequenom needs to prove itself a winner in more than just its Down's syndrome test. CAPS user dwh5056 thinks multiple, smaller revenue streams will be much more important to the biotech:

Extreme gap down in April overdone. Company has huge potential with new revenue generating products being release this year through early next year with potential revenue of $750 million / year. Company expects to be cash flow positive in 2010. A lot more reasons as well to be bullish.

Of course, even with the promise of these other tests, if Sequenom fails to recreate the positive data originally found with SEQureDx, investors must realize that their shares will undoubtedly be crushed again. Whatever the company's longtime value may be, in the short term, much will depend upon the outcome of the Down's syndrome results.

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.

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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 gold-plated disclosure policy.