While large-cap stocks might not have as much upside potential as smaller companies, these behemoths can still be excellent wealth generators over the long term. More importantly, that value creation often comes with less risk for the investor because these companies have established themselves as market leaders. While there are several large-cap stocks to choose from, three that caught our eye as having the potential to deliver outsized gains in the years ahead are Amazon.com (NASDAQ:AMZN), Wal-Mart Stores (NYSE:WMT), and Enbridge (NYSE:ENB)

A retailer with staying power

Rich Duprey (Amazon.com): Because Amazon.com has altered the retail landscape and redefined how an e-commerce company should operate -- as well as changing even how we think about such businesses -- it's a good bet that we'll continue seeing the online retail king transforming itself and its industry well into the future.

Concept of business man drawing growth chart for the year 2020.

Image source: Getty Images.

When considering an Amazon investment, though, it's necessary to toss out all standard valuation models. You can't look at price-to-earnings ratios or similar metrics because almost since its appearance on the public stage 20 years ago, it has seemed overvalued. And because it continues to shift and evolve over time, knowing what to look at becomes exceedingly difficult.

For example, who could have predicted that a simple online bookseller would become a critical cloud-based web services provider powering the businesses of major corporations worldwide; would operate its own fleet of aircraft to handle the logistics of delivery; would become the biggest apparel retailer; and would be able to buy the foremost organic food retailer, Whole Foods Market (NASDAQ:WFM)?

What does seem clear is that stasis is not in Amazon's DNA, and that the one constant is change. But even so, its position as the premiere online retailer will only grow. During the holiday season, for example, Slice Intelligence reported that the e-commerce site accounted for half of all U.S. online sales on the Monday before Christmas, and it had a 38% share for the holiday season overall. That's going to grow as sales continue to move online and the death of the shopping mall becomes more apparent.

Amazon's importance to the fabric of the economy will become further ingrained and its stock will continue to rise, regardless of current valuation.

Don't sleep on this giant

Daniel Miller (Wal-Mart): It's pretty incredible to think how quickly the world -- and business in general -- moves these days. Because of that, it's easy to forget how dominating and cutting-edge Wal-Mart's scale, pricing power, and distribution were two decades ago when it was crushing every chain in its path. Since then, the world has surged in terms of technology and e-commerce, and many investors now consider Wal-Mart outdated. But you shouldn't make that mistake.

We already know that Wal-Mart is the largest retailer in the world by revenue. That simply means that few retailers can even compete with the company's scale and pricing power. We already know that Wal-Mart is essentially a one-stop option in the brick-and-mortar world. But to be successful for the long term, Wal-Mart needs to focus on its e-commerce, and it's absolutely doing that.

With its acquisition of Jet.com and free two-day delivery on qualified products, Wal-Mart is attempting to take a page out of Amazon's book in hopes of drastically boosting user traffic to the company's e-commerce websites. With Wal-Mart's massive locations, which number around 11,700, it has the network to competitively distribute products from its stores to nearby customers for its online sales, as long as it creates the technology to effectively and efficiently connect the dots. If it can, it shouldn't be out of reach for Wal-Mart to drive its online sales around 30% annually through the remainder of this decade.

Wal-Mart used to be a massive retailer with a simple online website. That's no longer the case -- and it's trying new concepts as well. Its e-commerce struggles are turning around quickly, and with its scale and distribution advantages already in hand, the company is well-positioned to succeed over the long term.

Woman on couch shopping on her cellphone.

Image source: Getty Images.

Always looking ahead

Matt DiLallo (Enbridge): While most companies focus on short-term goals, such as meeting quarterly earnings guidance, energy infrastructure giant Enbridge sets its gaze on the long term. That's evident by the length of its current growth projections. While many of its pipeline rivals don't provide investors with a dividend growth forecast, Enbridge expects to increase its payout by double digits all the way through 2024, which is by far the longest forecast in the sector.

Driving that forecast is the company's sector-leading backlog of growth projects, which includes 26 billion Canadian dollars ($19.6 billion) in execution and another CA$48 billion ($36.2 billion) under development. Since these are primarily fee-based and regulated assets, Enbridge anticipates that its cash flow will steadily rise as these projects enter service. Furthermore, it's worth noting that while many of those projects are oil pipelines, Enbridge has been focusing more attention on investments in cleaner energy solutions, including natural gas pipelines and offshore wind farms, which make up more than half of the projects it has in development.

Enbridge's recent focus on wind investments is particularly noteworthy because these facilities generate returns that are as good as new oil pipelines -- if not better. Meanwhile, the sector is expected to grow at a faster pace than fossil fuels, providing Enbridge with plenty of potential growth opportunities in the years ahead. As Enbridge captures more of these opportunities, it could allow the company to continue growing faster than rivals, which makes it an excellent stock to own for the long term.

John Mackey, CEO of Whole Foods Market, is a member of The Motley Fool's board of directors. Daniel Miller has no position in any stocks mentioned. Matt DiLallo owns shares of Amazon and Whole Foods Market and has the following options: long January 2019 $55 calls on Wal-Mart Stores, short January 2018 $72.5 calls on Wal-Mart Stores, and short November 2017 $34 calls on Whole Foods Market. Rich Duprey has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Amazon, Enbridge, and Whole Foods Market. The Motley Fool has a disclosure policy.