For years now, much of Wall Street has believed that legal marijuana is the greatest investment opportunity since sliced bread. Investors are fully aware of the massive black market and understand that ongoing legalizations around the world could move tens of billions of dollars into legal channels in the years to come. That could allow cannabis stocks -- and investors -- to see plenty of green.

But the nascent legal marijuana industry has also been hit with a flurry of early stage problems. A large backlog of licensing applications with Health Canada has significantly constrained how much pot growers can producer or harvest. Likewise, a shortage of compliant packaging solutions has left unfinished cannabis on the sidelines waiting to be processed.

Cannabis buds lying atop a messy pile of cash.

Image source: Getty Images.

We've also witnessed supply and tax issues rear their head in the United States. California's first year of recreational pot sales came in well below expectations in terms of sales and tax revenue. A slower-than-expected approval of dispensary licenses by the state, grower oversupply, and high tax rates that have led to the persistence of the black market have all played a role in the Golden State delivering disappointing cannabis revenue.

As a result, while sales for publicly traded pot stocks are still expected to soar in 2020, revenue estimates are a lot tamer now than they were, say, six months ago. In fact, of the 60 pot stocks I track on a regular basis, just six are expected to generate in excess of $500 million in sales in fiscal 2020.

These five well-known marijuana stocks should top $500 million in 2020 sales

Five of the six names are companies you'd likely expect to find as top revenue producers. For example, the three largest marijuana growers by peak annual output -- Aurora Cannabis (NYSE:ACB), Canopy Growth (NASDAQ:CGC), and Aphria (NASDAQ:APHA) -- rank fourth, second, and third, respectively, in fiscal 2020 sales, based on Wall Street's consensus. Aurora Cannabis should be yielding 625,000 kilos on an annual run-rate basis by the end of fiscal 2020 (June 30, 2020), with Canopy Growth likely pushing north of 500,000 kilos yearly, and Aphria hitting its max annual output of 255,000 kilos by the midpoint of 2020.

Canopy Growth is expected to generate close to $580 million in 2020 sales, although the company will still be losing quite a bit of money as it expands into overseas markets and builds out its infrastructure. Aphria, with a consensus estimate of $552 million in revenue, should be profitable, according to Wall Street. The big question mark is when the company's flagship Aphria Diamond facility will receive its cultivation license from Health Canada. And then there's Aurora Cannabis, which despite $552 million in expected sales, may wind up losing money as it also expands its infrastructure.

A vial of Epidiolex next to its packaging and two droppers.

Image source: GW Pharmaceuticals.

Cannabinoid drug developer GW Pharmaceuticals (NASDAQ:GWPH) is the consensus No. 6 pot stock, with expected sales of $511 million. GW Pharmaceuticals launched Epidiolex, the first cannabis-derived and FDA-approved drug, in early November, and looks to have a clear runway to sales in one of the two indications it was approved. In clinical trials, GW Pharmaceuticals' lead drug reduced seizure frequency from baseline by 30% to 40%, making it easy for the FDA to give this groundbreaking medicine the green light.

U.S. multistate dispensary operator Acreage Holdings (OTC:ACRGF) also makes the list at No. 5, with 2020 sales forecast at $542 million. Acreage, which has retail, processing, or manufacturing licenses in 20 states (on a pro forma basis), has agreed to be acquired by Canopy Growth on a contingent-right basis. The condition of Acreage's acquisition is that the U.S. government legalizes marijuana at the federal level.

This surprising pot stock may lead all cannabis stocks in 2020 sales

None of the five aforementioned marijuana stocks with projected sales of at least $500 million in 2020 should come as a surprise to investors. But what may indeed shock you is learning which company Wall Street's consensus sales estimates currently peg as the leading revenue producer in fiscal 2020.

Drumroll, please: Cresco Labs (OTC:CRLBF).

Not only is Cresco Labs tops in 2020 sales, according to forecasts, but it's not even close. Whereas No. 2 Canopy Growth and No. 6 GW Pharmaceuticals will generate $580 million and $511 million in sales, respectively, Cresco is in another zip code, with $738 million in projected 2020 revenue. And don't think for a moment this figure is the result of a rogue analyst going off the rails. The four locked-in sales estimates for 2020 range from $670 million to $775 million.

A gloved processor holding a freshly trimmed cannabis bud in their outstretched left hand.

Image source: Getty Images.

So why is Cresco Labs and not, say, Canopy Growth at the top of the sales pecking order? A big reason could be Cresco's two-pronged attack.

First, Cresco is in the process of acquiring Origin House (OTC:ORHOF) for what was an $823 million all-stock deal when first announced at the beginning of April. Origin House holds the distinction of being one of the very few cannabis distribution license holders in California. Being in this niche position will allow Cresco to benefit from distribution revenue in the biggest pot market in the U.S., as well as push its in-house-branded products into more than 500 California dispensaries. The deal has already been approved by Origin House shareholders and now awaits the OK from the U.S. Justice Department.

Second, on top of benefiting from Origin House's key distribution position in California, Cresco Labs holds 56 retail licenses and 23 grow farm licenses spanning 11 states. As a multistate dispensary operator in some of the United States' largest markets, it should see a significant uptick in sales as it aggressively pushes to open new retail stores.

It remains to be seen if Wall Street's forecasts prove accurate, but for the time being, it's Cresco Labs -- not Canopy, Aurora, or Aphria -- that's the king of the cannabis hill for 2020.

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.