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.

Some of these names might surprise you, since you've probably put a tiger in your tank at an Exxonstation at one time or another, maybe even as far back as when it was called Esso. Almostgreat? 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?
As rumors of a possible takeoversubside, Energy Conversion Devices' shares have sagged as well. The disruptions to the global economic, financial, and credit markets continue to pressure solar investments, while flagging government support through subsidies means that future system sales could be in jeopardy.

A recent Associated Press story noted that it's never been cheaper than now to buy a solar power system. Between federal, state, and utility subsidies, the cost of purchasing a system can be cut by as much as 90% in some areas. Foreign governments have subsidized the cost of solar power as well, but they've also started reducing or eliminating their payments, and that's causing consternation in the industry.

A solar sunset
Germany has proven to be the world's largest market for solar power, no doubt largely because of the subsidy program in place there, which guarantees renewable energy generators fixed payments for the power they produce. However, critics contend that the program simply drove up the cost for electricity, and Germany is now set to cut the subsidy program considerably. Spain is another country that heavily relied upon subsidies to get solar moving, only to eventually derail the gravy train. And Ontario, Canada, introduced new subsidies that use protectionist trade language and feature land-use regulations that will hamper some solar companies from developing many new projects there.

First Solar (Nasdaq: FSLR), for example, says that if Ontario doesn't significantly modify its domestic content rules, its ability to participate in the feed-in-tariff program for future projects could possibly be completely eliminated. Energy Conversion Devices doesn't have much of a presence, if any, north of the border, but nearly one-fifth of its revenues came from Germany last year, meaning subsidy cuts there could result in reduced demand. How the U.S. handles its handouts could also cause an impact.

Suntech Power , Energy Conversion Devices, and First Solar are among the companies whose investors have found that without the helping hand of government, they simply can't compete with other forms of energy. With solar also facing a supply glut of polysilicon, wafers, and PV panels, it may just take industry consolidation to sort out the problems.

That's an outcome that looks to be picking up steam. LDK Solar (NYSE: LDK), ReneSola (NYSE: SOL), and MEMC Electronic Materials have all picked up small, privately held companies to help them become more vertically integrated. Continued...