While there's no sure thing when it comes to investing in the stock market, finding those golden eggs that could usher your portfolio into the seven-figure club isn't as complicated as you might think. Whether or not a stock has millionaire-maker potential depends on a wide range of factors. These include the company's competitive advantage, its growth prospects, the durability and value of its products and services, its long-term financial performance, and how much you invest in the particular stock and when.

If you're on the hunt for superior investment plays that could make a serious difference in your journey to wealth-building through the stock market, you've come to the right place.

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1. Teladoc

Few stocks garnered as much attention at the height of the pandemic market than Teladoc Health (TDOC -4.67%). The virtual healthcare giant has recorded astronomical platform growth throughout the pandemic as people are increasingly leveraging digital solutions for essential and non-essential medical care.

The stock spiked from trading around $175 per share one year ago to just under $300 at its peak this past February. Now, shares are trading at a discount of approximately $180. Should this downtick in Teladoc's share price concern investors? Absolutely not. Teladoc's share price alone isn't an indicator of its overall viability and strength as an investment. In fact, factors that do inform the long-term upside potential of an investment -- such as competitive advantage in its industry, balance sheet strength, and future growth prospects -- remain stronger than ever in Teladoc's case.

Teladoc is one of the most prominent players in the global telemedicine scene, and this industry is expected to continue expanding at a rapid pace in the years ahead. According to a Jan. 2021 report by Fortune Business Insights, "The market is projected to grow from USD 79.79 billion in 2020 to USD 396.76 billion in 2027." The report also notes that virtual healthcare "not only helps patients to connect with physicians remotely but can also aid in reducing the cost burden of healthcare," which is both leading an increasing number of medical providers to offer this option to patients and effecting changes at the federal government level to incentivize the use of digital health solutions.

Teladoc's growth potential is already evident as the world moves ever closer to the post-pandemic era. 2020 was without a doubt a great year for the company. Not only did its full-year revenues surge by nearly 100%, but total visits on its platform soared by a triple-digit percentage.

Teladoc kicked off 2021 on a high note though, marking another rock-solid period of growth in the first quarter of the year. During this three-month period, its revenues spiked 151% year over year and total visits on its platform increased 56%. In addition, Teladoc's U.S. paid memberships jumped 20% from the year-ago period. CEO Jason Gorevic noted: "Consumers are embracing our whole-person virtual care offerings, engaging with multiple products and coming to us for more of their health needs."

Management is forecasting continued strong growth in the second quarter and also raised its full-year guidance on the heels of its stellar first-quarter results. The company is forecasting total revenue between $495 million and $505 million in the second quarter and full-year revenues in the ballpark of $2 billion. There's no telling how far Teladoc's growth story could take it over the next few decades, and long-term investors who stay along for the ride could bag some life-changing returns in the process.

2. Intuitive Surgical

Intuitive Surgical (ISRG 0.18%) is leading the way in the field of medical robotics, and its da Vinci surgical system is used by healthcare providers around the world for a broad spectrum of minimally invasive surgical procedures. Shares have continued to rise slowly throughout the pandemic, and Intuitive Surgical is now trading approximately 70% higher than it was just one year ago.

Intuitive Surgical's full-year revenues declined slightly in 2020 compared to the previous year, which wasn't at all surprising given the widespread trend of fewer surgical procedures being performed at the height of the pandemic. But the last two quarters have marked a pattern of steady recovery to the company's pre-pandemic growth levels.

In the fourth quarter of 2020, Intuitive Surgical reported that worldwide da Vinci procedures jumped 6% while its base of installed systems increased 7% year over year. In total, the company's fourth-quarter sales grew 4% from 2019.

Intuitive Surgical's first-quarter 2021 financial performance further soothed investors' nerves as it continued its strong recovery from pandemic-induced headwinds. During this period, the company's worldwide da Vinci procedures increased 16% and its base of installed systems went up 8% from the year-ago stretch.

Intuitive Surgical also shipped out 26% more da Vinci surgical systems to customers than in the first quarter of 2020, while its revenues spiked 18% year over year. Intuitive Surgical also grew its bottom line 37% from the year-ago period.

Analysts project that Intuitive Surgical will faithfully report double-digit earnings growth over the next half-decade alone, which will likely also be reflected in its share price. Also consider that the global medical robotics market is set to reach a valuation of more than $16 billion by the year 2025. Intuitive Surgical's growth story is just getting started, and now is an excellent time for long-term investors to jump on the bandwagon and scoop up this foolproof stock.

3. Pfizer

A classic pick for healthcare investors, Pfizer (PFE 0.76%) is one of those companies you can buy and hold in your portfolio forever. The company boasts a robust dividend, which currently yields about 4% for investors. Pfizer has slowly but steadily increased its dividend over the past decade as well, it recently gave a 3% boost to its first-quarter dividend.

The company reported 3% revenue growth on an operational basis for the full-year 2020, led by 8% operational growth in its flourishing biopharma business segment. Its top-selling products within this segment last year were oncology and rare disease drugs, with full-year revenues from these two areas surging 21% and 29%, respectively. The fourth quarter was a particularly impressive period of growth for Pfizer, and its total revenues surged 11% in the three-month period.

It's also important to note that Pfizer's biopharma segment is slated to experience significant growth in the coming years on the heels of its COVID-19 vaccine success. The vaccine -- demonstrating 95% efficacy at late-stage clinical trials and 91.3% efficacy up to six months post-vaccination, according to updated top-line data -- is set to rake in revenues for Pfizer to the tune of $15 billion in 2021 alone.

Pfizer has already established a lucrative roster of supply deals for its coronavirus vaccine, and is about to sign a landmark agreement with the European Commission that would mean many billions more in revenue for the company.

Shares of Pfizer have remained relatively steady despite the onslaught of headline-leading developments that it's reported in recent months, and the stock is trading right about where it was one year ago. Historically, Pfizer's track record of persistent, incremental balance sheet growth in all manner of market environments has also translated to slow but steady share price gains. This pattern should continue in the years to come, making it an unstoppable investment to have in your basket of stocks in both bull and bear markets. 

In addition, Pfizer's robust payout could also be a source of serious portfolio gains for dividend investors who are in it for the long haul. There's never been a better time to buy shares of this incredibly affordable healthcare stock to prime your portfolio for sustainable growth for decades.