Lots of investors enjoy looking for unique growth opportunities most other people have yet to find. The fact is, however, the pillars of your portfolio are going to look quite a bit like the big winners found among everyone else's holdings. The better the prospect, the more likely it is its story is already being told.

The thing is, that's OK. A winner is a winner no matter how many other people own it.

Here's a look at three unstoppable investments most everyone should be holding in their long-term portfolios. Each is built to last, and more than that, each is positioned to continue dominating its respective market.

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1. Walt Disney

Media giant Walt Disney (NYSE:DIS) isn't a name that needs much of an introduction. From television to toys to theme parks (and more), this company's got exposure to a lot of different businesses. And, the mix works -- Disney is also a powerhouse in each of the markets it operates in.

That's not entirely clear in light of last quarter's results. While the company showed the expected improvement compared to last year's COVID-19-crimped fiscal Q4 numbers, streaming subscriber growth slowed to a crawl. Its flagship streaming platform Disney+ only added 2.1 million paying customers during the quarter, falling well short of estimates. For a company that completely restructured itself a little over a year ago to focus on cultivating its streaming business, that's a problem.

Except maybe it isn't.

While last quarter was admittedly lackluster, keep it in context. The coronavirus pandemic is still with us, standing at least somewhat in the way of consumer-facing companies, as well as stifling television and film production. Disney's said nearly a year ago that it's got nearly a couple dozen Star Wars and Marvel-based television series planned for Disney+, most of which have yet to arrive on the platform. As these shows make their way to the streaming venue, look for interest in the service to perk up again. In the meantime, embrace the fact that the Disney brand name itself is one of the most powerful ones on the planet.

2. Microsoft

Software name Microsoft (NASDAQ:MSFT) is arguably as recognizable as Walt Disney; you may even be a customer yourself. It's the Microsoft you don't know, however, that makes this stock such a solid, easy pick for a newcomer to own.

Sure, Microsoft is still the outfit behind the Windows operating system, which according to GlobalStats' Statcounter is installed on 75% of the world's conventional (non-tablet/non-phone) computers. It's also the developer behind the "Office" suite of productivity software, in all of its variations. Although tons of alternatives -- many of them free -- have surfaced over the course of the past several years, Microsoft's share of this space remains healthy.

Did you know, however, that Microsoft is also in the businesses of cloud computing, professional networking, video gaming, and web search as well? It's true. Research outfit Canalys estimates that Microsoft's cloud-management software Azure has allowed Microsoft to take control of 21% of the world's cloud infrastructure market. This business is still growing too. Leveraging the popularity of Azure, last quarter's Intelligent Cloud division saw revenue grow 31% year over year to $17.0 billion. Meanwhile, office productivity software revenue grew 22%, while Microsoft's LinkedIn top line improved by 39% year over year.

As long as consumers and corporations continue to use almost any sort of technology, you can expect this company to successfully capitalize on that demand.

3. Nvidia

Finally, add Nvidia (NASDAQ:NVDA) to your list of unstoppable stocks to consider if you're new to the investing game.

As was the case with Microsoft, there's the Nvidia you know -- Nvidia is best known for its computer graphics cards and other display technologies. That's not all the company does, though. Self-driving cars, computer visualization solutions for professionals, and even data centers are all in this company's wheelhouse. In fact, last quarter's data center revenue of $2.9 billion was almost as much as the gaming business Nvidia did, accounting for more than 40% of its top line.

And that's just the beginning if technology market research company Technavio's outlook is on target. Technavio forecasts the data center market will grow at an annualized pace of 21% through 2025. It will also be led by spending on artificial intelligence systems, where Nvidia excels; eight out of the world's ten most powerful supercomputers are already built around Nvidia hardware. In this vein, another market research company called Omdia reports Nvidia is currently doing about 80% of the world's A.I. processor business.

Data centers aren't the only big long-term growth opportunity for Nvidia either. Although its autonomous driving arm only collected $135 million worth of revenue last quarter, this business is on the verge of exploding. Deloitte notes the consensus estimate that more than 30 million autonomous vehicles will be sold in 2040, versus only 1 million 2025 and practically none now. Advanced driver-assistance systems, or ADAS, are more common now but are still only found on a small number of new cars being sold. That's a big growth opportunity too.

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.