Success attracts attention. If you have any doubts about it, just look at the list of the 100 most popular stocks on Robinhood (HOOD 3.37%) right now.

Many of them delivered market-beating returns this year. And some of the most popular ones generated sizzling gains. The more they rose, the more investors on the trading platform turned to them. Here are 10 top Robinhood stocks that doubled (or more) in 2021 -- and whether or not they're smart picks to consider buying now.

An arrow with a dollar sign hanging from it stuck in the bullseye of a target.

Image source: Getty Images.

Robinhood's doubles

As you might expect, several meme stocks made the list of the popular Robinhood stocks that doubled this year. But there are also a few that might be surprising.

Stock

Market Cap 

2021 Gain 

AMC Entertainment (AMC 8.23%) $15.3 billion 1,280%
GameStop (GME -3.94%) $12.1 billion 725%
Lucid Group (LCID -2.86%) $64.6 billion 290%
Globalstar (GSAT -0.79%) $2.1 billion 247%
Ocugen (OCGN -6.06%) $966 million 163%
Marathon Oil (MRO 0.55%) $12.9 billion 146%
Moderna (MRNA 3.01%) $101.9 billion 143%
Ford Motor Company (F 6.10%) $82.6 billion 133%
Nvidia (NVDA 4.35%) $747.9 billion 128%
Catalyst Pharmaceuticals (CPRX -0.20%) $731 million 108%

Data sources: Robinhood, Yahoo! Finance, YCharts.

Only three of these top Robinhood winners began 2021 as small-cap stocks: Catalyst Pharmaceuticals, Globalstar, and Ocugen. Two of them were still under the $2 billion threshold at the end of the year.

Nvidia proved that elephants can dance after all. The mega-cap stock ended the year as a huge winner.

Most of these stocks are well off their highs set in 2021. Four of them -- AMC, GameStop, Globalstar, and Ocugen -- are down more than 50% from their peak levels.

Ones to avoid

AMC and GameStop have especially been like lightning rods this year, attracting fervent supporters and sometimes equally fervent detractors. You wouldn't want to touch an actual lightning rod. I think staying away from AMC and GameStop is also wise.

While the stocks have skyrocketed, their businesses haven't performed nearly as well. Neither AMC nor GameStop have returned to pre-pandemic levels. GameStop is losing money faster than ever.

Wait for now

A few of the high-flying Robinhood stocks of 2021 could still be worthy of consideration in the future, but not just yet. I'd put Moderna at the top of that list. The company's messenger RNA platform holds tremendous potential in developing vaccines and therapies targeting a wide range of diseases. For now, though, Moderna's fortunes hinge on what happens with COVID-19. The outlook on that front remains uncertain.

Another COVID play, Ocugen, is on even more treacherous ground. The company hopes to win authorizations or approvals in the U.S. and Canada for COVID vaccine Covaxin. However, the wait continues. Until there's more reason for optimism, I'd stay on the sidelines with this stock.

Globalstar's shares surged earlier this year on speculation that Apple's next iPhone would support satellite communications. Those rumors didn't pan out. I wouldn't dismiss the possibility that future iPhone versions could be satellite phones, though. Globalstar would likely be a big winner if that's the case. 

Some investors think Lucid could be the next Tesla. Maybe it will. My view is that a wait-and-see approach is best.

Consider buying

So are there any popular Robinhood stocks that doubled or more in 2021 that are worth a hard look? I think four of them deserve consideration.

I'll start with the riskiest of the group. Catalyst Pharmaceuticals has all of its marbles riding on the commercial success of Firdapse, a drug approved to treat rare autoimmune disorder Lambert-Eaton myasthenic syndrome (LEMS). U.S. sales are soaring for Firdapse. If Catalyst can secure regulatory approvals in other markets, the stock could keep its momentum going.

Marathon Oil is another stock that just might continue its winning ways. As the global economy recovers from the pandemic, demand for oil and gas should rise. That should be great for Marathon, which still trades at only 9.3 times expected earnings even after its huge gain this year.

My Motley Fool colleague Will Ebiefung picked Ford as his top stock to buy in December. The month is at its end now, of course, but Will's rationale for buying the automaker still holds true. Ford's shares remain cheap with a forward earnings multiple of 10.5. The company is also poised for success in the electric vehicle market.

Nvidia ranks as my personal favorite among these top-performing Robinhood stocks. The company should continue growing robustly as the demand for its graphics chips increases. In particular, I view Nvidia as a great stock to buy to profit from the metaverse as it's built out.