One of the stock market's most successful companies over the past 10 years, eBay has gone on to reward investors with market-beating returns. The opportunity for eBay's sales to continue growing remains, however, our Motley Fool contributors think investors will benefit more if they own MercadoLibre (MELI 1.96%), Shopify Inc. (SHOP 4.90%), and Boeing (BA -0.76%) in portfolios. Read on to find out why these stocks could be poised to produce envy-inspiring gains for investors.

Same game, different place

Dan Caplinger (MercadoLibre): eBay has been a solid performer, having more than doubled in price over the past decade. Yet MercadoLibre, which operates in a similar business in Latin America, has dramatically outpaced eBay's stock returns, posting gains of nearly 450% over that same timeframe.

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MercadoLibre has found success largely by duplicating much of what made eBay great. The Latin American company started by creating an online marketplace where users could buy and sell goods. Over time, MercadoLibre added related services to complement its users' e-commerce experience, including the MercadoPago electronic payments platform and the MercadoEnvios shipping service. Most recently, MercadoLibre has offered financing options to buyers. Because Latin America has seen faster growth rates than the U.S., especially in its consumer base, MercadoLibre has seen its fundamental performance outpace that of eBay.

That's not to say that MercadoLibre doesn't face risk. Some fear that U.S. e-commerce giants will seek to penetrate the Latin American market more fully, threatening MercadoLibre's dominance. Yet with a well-established home-field advantage, MercadoLibre's rivals won't find it easy to upend the leading e-commerce player in the region. With shares having fallen recently due to those fears, investors have the rare opportunity to invest in shares of MercadoLibre at a relative bargain price.

A sizzling hot e-commerce stock

Todd Campbell (Shopify Inc.): It may seem that Internet retail has overtaken traditional retail as the main way consumers buy things, but the reality is there's still a tremendous amount of room left to grow. The Census Bureau pegs e-commerce at less than 10% of total retail spending in the U.S. and it represents an even smaller slice of retail in other countries.

Price and convenience advantages will support more retail shopping moving online and that will undeniably benefit eBay, but I think Shopify's going to grow more quickly.

Unlike eBay, which provides individuals and businesses a centralized e-commerce solution, Shopify is decentralized. Its solutions allow small businesses to create a professional-looking e-commerce site quickly that can be integrated easily with traditional brick-and-mortar inventory systems. Once a site is built on its platform, Shopify customers can sell products through any number of online distribution partners, including Amazon.com, Facebook, and as of July, eBay. Shopify provides financing and payments processing, too.

Shopify reports Q3, 2017 earnings tomorrow, but in Q2, total revenue was $151.7 million, up 75% from Q2, 2016. Subscription solutions revenue grew 64% to a record $71.6 million as more customers translated into greater monthly recurring revenue. Merchant solutions revenue grew 86% to $80.1 million because customers sold more products. A total of $5.8 billion in products were sold in the quarter, up 74% year over year. While growth could vary quarter-to-quarter, the long-term potential for this company is massive. After all, eBay's quarterly sales and product volume are $2.4 billion and $20.5 billion, respectively.

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Labor's loss is investors' gain at Boeing

Rich Smith: (Boeing): eBay's returns have been good this past year, no doubt. Up 27% over the past 12 months, this one-time "internet economy" darling is easily beating the S&P's performance (which is up less than 20%). eBay's done even better over the past five years, rising 67% in price over that period. But would you believe that Boeing has done even better?

Fact is, over the past year alone, Boeing stock has risen in value more than eBay's stock has in the past five years -- up 77%. In an apples-to-apples, five-year comparison, Boeing looks even better, having risen in value nearly 250%.

How has Boeing done this, and can Boeing keep on doing it? Some might attribute Boeing's success solely to the big boom in aircraft sales earlier this decade. But airplane industry watchers know that this boom has slowed "significantly" of late.

Boeing knows it can't rely on an infinite boom in airplane demand to keep its business flying high. That's why, in 2014, Boeing made a strategic (and in my view, brilliant) move to pre-emptively lock in low labor rates with its machinists union through 2024. For nearly the next seven years, Boeing should have little difficulty keeping its costs low -- and its profits flying high. I'd expect Boeing stock to fly pretty high, too.