Sometimes, the best investments are right in front of us. I believe this is the case today with Amazon (NASDAQ:AMZN).

The $1.7 trillion e-commerce and cloud-computing giant may have already helped compound shareholder capital significantly. But investors shouldn't count this megacap stock out yet when it comes to potential investment returns. Amazon is still in growth mode -- and its shares are trading at a surprisingly reasonable valuation in relation to its long-term prospects.

Here's why Amazon is a great growth stock for investors to consider buying today.

A person looking at charts on a laptop.

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E-commerce is just getting started

Sure, Amazon's $386 billion in 2020 revenue may seem like an awful lot. Some investors may even wonder how there's still upside for the company's top-line figure. But consider this: Global retail sales are estimated at around $25 trillion annually, with about $6 trillion in the U.S. Yet e-commerce only accounts for about $4 trillion of global retail sales and less than $1 trillion of U.S. retail sales. 

Unsurprisingly, e-commerce is expected to grow as a percentage of overall retail sales in the coming years. eMarketer estimates that e-commerce's share of global retail sales will increase from 18% in 2020 to almost 22% by 2024. Given e-commerce's low penetration of global retail sales and its trend of taking greater share of global retail sales over time, there's still likely a lot of room for Amazon to grow its sales.

Of course, it's worth noting that not all of Amazon's sales come from e-commerce. Over $45 billion of the company's 2020 revenue, for instance, came from cloud computing -- a market that's growing even faster than e-commerce.

Strong fundamentals

Beyond this high-level look at Amazon's e-commerce market opportunity, the company's financial performance notably speaks for itself. Total sales climbed 38% year over year in 2020, with net income surging from $11.6 billion to $21.3 billion. This strong net income growth in 2020 came even though the company spent billions of dollars on COVID-19-related costs.

Of course, Amazon benefited from the strong tailwind of consumers sheltering at home in 2020 and turning to e-commerce to replace some of the items they previously bought at brick-and-mortar stores. But it's worth noting that management is still seeing strong momentum going into 2021. Management guided for first-quarter revenue to increase 33% to 40% year over year.

Amazon trades at about 80 times earnings today. But the company's strong lead in both e-commerce and cloud computing, top- and bottom-line momentum, and large addressable markets for continued growth over the next 10 years make this a fair (if not great) price to pay.

Sure, there's bound to be some downturns in the stock price from time to time. But the stock looks like an attractive buy today for investors willing to hold shares for the long haul.

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.