Some companies are obviously great investments -- in hindsight. Sure, we should have bought Starbucks at its IPO, earning returns in the hundreds of percent over the years. 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 companies in the CAPS universe, 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:

  • Alvarion (NASDAQ:ALVR)
  • JA Solar Holdings (NASDAQ:JASO)
  • NYMEX Holdings (NYSE:NMX)
  • Toyota Motors (NYSE:TM)
  • Yingli Green Energy (NYSE:YGE)

Some of these names might surprise you. Toyota isn't exactly an unknown anymore; now it jockeys with General Motors for top automaker honors. Yet sometimes the most familiar names can offer the best opportunities, if only because we've begun to take their potential for granted. The 78,000 CAPS investors chose these companies as less obvious sources for tomorrow's great buys. Let's see why they might merit your attention.

A platform for change
The world's largest physical commodities exchange, the New York Mercantile Exchange, also boasts that it's the largest energy futures exchange and options contract exchange. Particularly in uncertain times like these, as the market suffers from extremes of volatility, exchanges like NYMEX and CME (NYSE:CME) enjoy the benefits of that turbulence. Their valuations increase as well, because it's understood that they can increase contract prices during such times. NYMEX recently announced it was instituting a number of per-contract fees, no doubt reflecting the greater demand from traders; electronic volume in November increased 87% over last year.

Yet the possibility of industry mergers has many CAPS players thinking that NYMEX's valuation still has plenty of upside. CAPS All-Star Allstar13913 speculated about that back in August: "I believe with future consolidation that they are an impressive acquisition target for NYSE and many other exchanges. I believe a bidding war might develop, where the shares will sell at a premium to their current price."

Although NYMEX Chairman Richard Schaeffer only recently denied that the company was in merger talks with NYSE Euronext (NYSE:NYX), he went on to say that with the industry consolidating, "we're willing to talk with different potential partners."

NYMEX will soon begin offering a trading platform for carbon emissions, a field analysts believe will become substantially lucrative. CME Group and NYSE Euronext are also exploring such platforms. NYMEX certainly has many catalysts that could propel its value.

A great opportunity for you
That's the bullish word on NYMEX, but do you agree? Are these four-star stocks still investment-grade material? On Motley Fool CAPS, you can give your input, which can ultimately influence how they're rated. Outperform or underperform, near-term or well into the future, your opinion counts.

Sign up today for Motley Fool CAPS -- it's free. Let's hear what you have to say about the great and almost-great companies that interest you.

NYSE Euronext is a Motley Fool Rule Breakers recommendation. Get a 30-day free trial to see all of the market-beating recommendations from any of the Fool's investment services.

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. Starbucks is a Stock Advisor selection. The Motley Fool has a disclosure policy.