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 rated 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 a handful:

  • KMG Chemicals (Nasdaq: KMGB)
  • Republic Airways Holdings (Nasdaq: RJET)
  • Flamel Technologies (Nasdaq: FLML)
  • Silicon Graphics International (Nasdaq: SGI)
  • Unilever (NYSE: UL)

Some of these names might surprise you. For example, you probably slather Hellmann's mayonnaise on your sandwich or lather up with Dove soap without even realizing you're using Unilever brands. 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 150,000-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?
Specialty chemical maker KMG Chemicals is making a bet that the tech sector is on its way back, paying almost $25 million to purchase an electronic chemicals business. KMG Chemicals supplies wet process chemicals used to clean and etch silicon wafers to the semiconductor industry. While it has a significant presence in Europe, with the acquisition, KMG Chemicals gains a further toehold in Asia while substantially increasing its share of the market here in the U.S., where it competes against Honeywell (NYSE: HON) and BASF.

The stock charged higher last year, more than tripling in value as the specialty chemicals business recovered from its recession lows. However, after hitting a peak of more than $19 a share in December (a level they hadn't reached since late 2007), KMG Chemicals shares have lost about 30% of their value. Investors looking at the company's pre-eminent position not only in semiconductor chemicals, but also wood preservatives and animal health pesticides, conclude that it will make for a strong addition to a portfolio.

CAPS member globalchem suggests KMG Chemicals'  pricing power will allow it to maintain its market share,  while JimVanMeerten is looking at the earnings track record.

About 92% of the CAPS members rating the company indicate it will outperform the market; share your thoughts on its future on the KMG Chemicals CAPS page.

On the shoulders of giants
When regional airline Republic Airways last week reported earnings that were substantially above last year's, its stock soared. While profits were below analyst expectations when you account for one-time items, it looks like Republic Airways ' acquisition of Frontier Airlines last year will be a solid addition to its portfolio as it offers larger airlines like Continental (NYSE: CAL), American, and Delta additional regional service in various markets.

CAPS member dnblack thinks Republic Airways looks something like a Clint Eastwood movie, The Good, The Bad, and The Ugly, and offers a cautionary note.

The Good:
-Massively undervalued (as in priced for [earnings per share] to shrink by 25% per annum for 5 years before flattening out).
The Bad:
-Massively in debt (as in 4.5 debt/equity). This will be particularly bad if we go into any sort of deflationary period as people seem to be speculating.
The Ugly:
-It is an airline (and losing its niche status by acquisitions). As [Buffett] puts it: "...the money that had been made since the dawn of aviation by all of this country's airline companies [is] zero."

A great opportunity for you
Some investors suggest 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.

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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. The Motley Fool has a gold-plated disclosure policy.