We Fools believe that holding great companies over long periods is the best way to grow wealthy. So which stocks do we think are great buy-and-hold candidates today? We asked that question to a team of investors, and they picked Activision Blizzard (NASDAQ:ATVI), Home Depot (NYSE:HD), and Spark Therapeutics (NASDAQ:ONCE).

Piles of money stacked up near a sand timer

Image source: Getty Images.

Play this one for years

Rich Duprey (Activision Blizzard): All stocks are judged on future expectations, and given Activision Blizzard's deep portfolio of game franchises, there's a good reason investors are excited about what tomorrow holds. They've bid up the video-game maker's stock 73% this year, as it continues to hit new record levels of active users.

Now if Activision Blizzard were just a video-game company, it would be easy to dismiss the stock as overblown, but as it evolves into a business seen as an entertainment company, one that can command and hold on to a user's attention for hours on end, it is every bit of a content-creation company in the vein of HBO, Showtime, and Netflix -- particularly in light of the creation two years ago of its own movie and television production studio that it hopes can help it transition the gamers to its theatrical releases. It released the first season of the animated TV series Skylanders Academy on Netflix in October 2016.

Moreover, because its games are delivered digitally as well as through brick-and-mortar stores, it can keep costs low while earning high margins. Analysts expect the game maker to be able to grow earnings at better than 20% annually for the next five years. That it trades at only 22 times next year's earnings estimates suggests Activision may not be priced as loftily as believed.

It's also quite likely the kids of today are quite familiar with Activision Blizzard, and having its stock in their portfolio as they grow with it will have them bragging about owning the stock even at these seemingly lofty heights.

This stock could pay for the home remodel

Demitri Kalogeropoulos (Home Depot): Home Depot is one of the biggest retailers in the country and is already worth over $170 billion in market capitalization. But that size doesn't mean the stock can't trounce the market over the ultra-long term from here.

Its operating results show no sign of slowing down as the housing industry's rebound marches on. Comparable-store sales growth was 6% last quarter, which not only marked an improvement over the prior quarter but also widened the gap between Home Depot and chief rival Lowe's. Importantly, Home Depot achieved that success through a healthy mix of rising customer traffic and higher spending per visit.

The retailer's most promising long-term growth possibilities include the industry segment that's made up of professional contractors and building specialists. It is also well positioned to build its online business up to an even bigger force.

There will be swings in Home Depot's business in the years ahead, given that it's so sensitive to the pace of broader economic growth. The current expansion doesn't seem close to ending, though. Long-term investors -- particularly those who allow their dividends to reinvest -- could accrue huge gains if this market leader continues dominating its industry while aggressively buying back shares and boosting its dividend payout.

A one-and-done philosophy

Brian Feroldi (Spark Therapeutics): Spark Therapeutics isn't for the faint of heart, but if everything goes according to plan, I could easily see it turning into a bragworthy investment.

Spark is a clinical-stage biotech focused on gene therapy. The company's big idea is to target diseases caused by faulty genes and to replace those genes with healthy ones. If the company can get the technology to work, it promises to cure some of the most troublesome diseases in the world.

Investors have a big catalyst to look forward to in early January that could go a long way toward validating the company's drug-development platform. Spark's lead compound, Luxutrna, has a PDUFA date of Jan. 12 as a hope treatment of vision loss from confirmed biallelic RPE65 mutation-associated retinal dystrophy. I'd wager the odds of success are quite good, because 93% of patients who used Luxutrna in a phase 3 study showed a gain in functional vision. Furthermore, no product-related serious adverse events were observed in the study, so safety shouldn't be a concern at all.

While Luxutrna is the most exciting drug for investors to watch, the company also has several other promising candidates in its pipeline that could turn into financial windfalls. The company has compounds that target other rare diseases, such as hemophilia, choroideremia, Batten disease, Huntington's disease, and more.

In total, Spark offers investors a potential game-changing drug-development platform and catalysts in both the near and long term. While clinical-stage biotechs always come with a fair amount of risk, the strong clinical data and upside potential Spark offers could make this a home-run stock in the making.