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.

  • Banco Santander (NYSE: STD)
  • Century Aluminum (Nasdaq: CENX)
  • Cirrus Logic (Nasdaq: CRUS)
  • Seagate Technologies (NYSE: STX)
  • Williams Companies (NYSE: WMB)

Some of these names might surprise you. For example, Spanish banking giant Banco Santander remains in good shape despite the crumbling finances of its country. Almost great? Even familiar names can still offer some of the best opportunities. Perhaps we've just forgotten the potential they still hold.

That's what's happened to natural gas pipeline company Williams Companies, which CAPS member altruria says realized the error of its ways, and got back to basics with drilling and distributing natural gas. 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?
With the market roaring out of the gate this morning as durable goods order showed surprising strength, we might expect that Century Aluminum and Alcoa (NYSE: AA) will go on to report better numbers down the road, as the production of durable goods are closely tied with aluminum. Excluding transportation orders, durable goods orders rose 2% compared to what the market was expecting, or just a 1% rise. Yet the airplane market is a big user of aluminum and softness there could be an issue if sales stay depressed. While transportation goods fell 10.3% last month, it would seem aluminum still has a pulse.

The CAPS community remains solidly behind Century Aluminum, as 92% of those rating the producer expect market-beating performance in the months ahead. You can add your ideas on whether aluminum is still malleable in this market on the Century Aluminum CAPS page and put it on your My Watchlist page to find all the Foolish news and analysis about the company.

On the shoulders of giants
Valuation would also likely be behind the failure of Seagate Technology to secure private equity financing to take it private again. Along with Western Digital, the drive makers sport minuscule market multiples, suggesting investors are just about looking for the drive industry to vanish. You have to respect storage peers STEC (Nasdaq: STEC) and EMC for their efforts, but the market is valuing these companies as if they had no future.

While the P/E firms Seagate was be in talks with supposedly didn't like that they were failing to hit performance numbers that had been set, that's become the public market's gain. At just three times trailing earnings (and Western Digital is at just four times last year's profit), Seagate investors could benefit from even a little bit of margin expansion. That could be why hedge fund operator Whitney Tilson of T2 Partners has taken a stake in the drive maker.

More than 1,100 CAPS members have weighed in on Seagate and 94% of them have rated it to outperform the broad market averages. While MashkiaTsair likes Western Digital's product better, he says you can't ignore how cheap Seagate's stock is.

A big opportunity
If you want to grow alongside a partner, choosing Apple as the one (or rather having them choose you) is a surefire winning strategy these days. With analysts projecting Apple to sell 21 million iPads next year -- more units sales than for its iMac -- you have an idea of the market opportunity for Cirrus Logic, which makes chips for the products. Analysts estimate Apple accounted for more than a third of revenues at Cirrus in the first quarter.

Moreover, despite its stock rising 171% in value over the past year, Cirrus Logic is trading at just 10 times next year's profits. No doubt the stock's recent declines have been on fears that it's come too far too fast, but boverby711 believes those concerns are much ado about nothing.

This has been falling now for a few weeks and the short interest is growing. I'm a lifelong contrarian and I think the fears baked into the market are overblown.

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.

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Fool contributor Rich Duprey currently does not own any stocks as you can see here. The Motley Fool has a disclosure policy.