How did Apple (NASDAQ:AAPL) do it? My son recently asked me for an iPod for his birthday. I figured he really meant to say that he wanted an MP3 player of any type, and I asked him if he wanted to try a Zune from Microsoft (NASDAQ:MSFT) or maybe a SanDisk (NASDAQ:SNDK) player. "Oh, no, Dad," he said in response. "It has to be an iPod."

And that explains why neither of those companies has been able to crack Apple's vise grip on the MP3 industry. It simply has to be an iPod.

But is the iPod really that superior as a product? Or is this more a result of great marketing and first-class product design? Or perhaps a combination of all three factors elicited his response. Whatever the case, Apple has managed to build up a sustainable competitive advantage for its iPod, and this has played a big role in delivering 86% annual returns for its shares over the past five years. How do we find similar growth stories for the next five or 10 years?

Recognizing the best
One way to consider if a company has a sustainable competitive advantage is to consider the trend of its return on invested capital (ROIC) over several years. Growing ROIC might indicate that the company has a superior product or service that has temporarily insulated it from competition. And such an advantage may result in outsized returns.

The following table looks at ROIC and annual returns for five companies, each with varying degrees of success in relation to its rivals. In the cases of Apple, Quality Systems, and Intuitive Surgical, increasing ROIC resulted in blockbuster annual returns over the same period. Great products can indeed result in great returns:

Company

FY 2003

FY 2004

FY 2005

FY 2006

TTM*

5-Year Annual Return

Apple

0.3%

4.4%

16.4%

17.6%

21.8%

86%

Quality Systems (NASDAQ:QSII)

19.2%

24.9%

33.1%

38.9%

34.4%

59%

Intuitive Surgical (NASDAQ:ISRG)

(3.0%)

4.7%

11.3%

13.0%

14.6%

73%

Celgene (NASDAQ:CELG)

(0.3)%

3.3%

5.6%

6.4%

10.1%

77%

Starbucks (NASDAQ:SBUX)

12.6%

15.0%

18.1%

18.8%

19.0%

20%

*Trailing 12 months. Data from Capital IQ as of Oct. 3, 2007.

The case of Apple appears to be a classic illustration of what a great product can do for a company. A mere four years ago, the company was languishing. We all know what has happened since then.

There's always a catch
Alas, the above is a backward-looking exercise, and the real key is to identify those companies with a sustainable competitive advantage before it is apparent to the vast majority of investors. Is it possible to foresee which products and concepts will dominate a particular industry?

David Gardner and his team of analysts at Motley Fool Rule Breakers would answer yes to that question. Their goal, in fact, is to spot the great businesses early on in their growth cycles and then hold those shares for the long term. This approach has already resulted in eight multibaggers -- names such as Intuitive Surgical and Vertex Pharmaceuticals -- since the service was launched in October 2004.

Looking at the trend of a company's ROIC is just one approach of many one might use when panning for investment gold. Each analyst at Rule Breakers has a unique way of identifying great companies, and thus far, I'm impressed with what they've unearthed. To see all of these great companies, take a free trial today. Just click here to get started.

This article was originally published on May 30, 2007. It has been updated.

John Reeves owns shares of Vertex Pharmaceuticals. And his son is really enjoying his iPod, especially after he deleted the boring songs his dad had downloaded before giving it to him. Quality Systems and Starbucks are Motley Fool Stock Advisor recommendations. Microsoft is an Inside Value pick. The Fool has a disclosure policy.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.