For the past 14 months, investors have enjoyed the strongest bounce back from a bear market bottom in history. After losing 34% of its value in just 33 calendar days during the first quarter of 2020, the widely followed S&P 500 has recouped all of its losses and rocketed to new highs. All told, the S&P 500 is up 44.4% over the trailing two years, which is a fantastic return that handily outpaces its long-term average.

But for some investors, a 44% return would represent mere peanuts. Folks who had the foresight, stomach, and luck to invest $50,000 into any of the following five names two years ago are now comfortably calling themselves millionaires.

A messy pile of one hundred dollar bills.

Image source: Getty Images.

GameStop: $1.12 million

It's the meme stock that started it all. Video game and accessories retailer GameStop (GME -4.41%) has managed to hold on to most of its gains from earlier this year, and as a result has returned more than 2,100% over the trailing 24 months. This means a $50,000 investment in mid-May 2019 is now worth a little more than $1.1 million.

Beginning in mid-January, retail investors on Reddit and other social platforms began banding together to buy shares and out-of-the-money call options in stocks with very high levels of short interest. The goal for these groups has always been to effect a short squeeze -- an event where pessimists feel trapped and scurry for the exit all at once. During GameStop's short squeeze earlier this year, shares catapulted from around $20 to nearly $500 in a matter of days.

Although GameStop was able to fatten up its balance sheet with a recent share offering, which will provide more than enough capital to oversee its ongoing transition to digital gaming, it's still facing two key challenges. First, its management team waited too long to begin shifting to digital gaming. This means GameStop's brick-and-mortar operations will remain a drag for years to come.

The other concern is that GameStop lacks the right recipe to still be a short-squeeze candidate. Its short interest has fallen dramatically since mid-January, and its higher average daily trading volume makes it unlikely that pessimists will feel trapped. In short, GameStop is really lacking for catalysts after its mammoth run higher.

A man holding a glowing golden locket that's surrounded by latticework representing blockchain nodes.

Image source: Getty Images.

Cardano: $1.15 million

It shouldn't come as a surprise that a number of cryptocurrencies have run absolute circles around the benchmark S&P 500. Though all the attention gets put on Bitcoin and Ethereum, Cardano (ADA -1.64%) has been a true outperformer. In fact, the 2,199% gain logged by Cardano over the trailing two-year period more than quadruples Bitcoin's return over the same time frame.

While I admit to being baffled by the valuations placed on digital currencies, at least Cardano enthusiasts have reasons to be excited. That's because this decentralized platform has a lot of ongoing development. For example, last summer the developers launched an upgrade known as Shelley, which increased the number of nodes that networks participants can run (i.e., it improved the decentralization of the network). Not long after this upgrade went into effect, Cardano went from averaging less than 2,000 transactions per day to averaging well over 30,000 a day last year. That's a positive sign of adoption. 

Equally exciting is the development of Goguen, which incorporates smart contracts onto the blockchain. Smart contracts are protocols that help to facilitate, verify, and enforce negotiated contracts between parties. If the name rings a bell, it's because smart contracts are what have made Ethereum so popular. 

Cardano may even be a featured investment vehicle by Grayscale, similar to how Grayscale has a trust for Bitcoin. The big question is: Will these catalysts prove sustainable? To that end, I'm not entirely sure.

A fanned pile of one hundred dollar bills transforming into digital currency.

Image source: Getty Images.

Takung Art: $1.52 million

Sometimes investors have to think small to win big. Once a penny stock, Takung Art (TKAT) has been one of the top performers over the trailing 24 months, racking up gains of over 2,900%. Had you invested $50,000 in mid-May 2019, you'd be sitting on more than $1.5 million today.

The bulk of Takung's massive gains have occurred since the year began. This upside has been fueled by the rise of non-fungible tokens, or NFTs. An NFT is a digital certificate of ownership placed on digital assets that are stored on blockchain in an immutable and transparent manner. In short, it declares someone to be the true and rightful owner of a digital asset.

Takung is an online platform that allows artists and art dealers to sell or trade artwork. Keep in mind that when I say artwork, I'm referring to everything from traditional paintings to items like sculpture and even jewelry. With an online platform already in place, investors are speculating that it would be easy for Takung to add NFTs.

The concern here is that this rise has been entirely based on speculation. Takung Art hasn't said anything about entering the NFT space, and its revenue has been in a relatively steady decline for the past five years. The company didn't even hit $4.6 million in sales last year after bringing in more than this in a single quarter in 2016. Suffice it to say, this gain looks unsustainable.

Multiple bicycle chains linked to a single source, representing blockchain technology.

Image source: Getty Images.

Chainlink: $2.26 million

One of the most robust investments over the trailing 24 months is under-the-radar cryptocurrency Chainlink (LINK -0.96%). Investors who purchased $50,000 worth of Chainlink in mid-May 2019 at less than $1 are relishing its current price north of $43. This greater than 4,400% return would have turned $50,000 into a cool $2.26 million.

What investors seem to like about Chainlink is the developers' interesting approach to further decentralizing blockchain networks. On traditional blockchain, sensors are set up to monitor and relay information to and from the blockchain. However, these sensors, known as oracles, are centralized, and therefore considered to be the weak link of blockchain networks. Chainlink has created the first blockchain oracle network, which verifies oracle authenticity and reconciles incorrect data (which can't be corrected on certain blockchains), all with the assistance of smart contracts. 

Additionally, Chainlink's blockchain is able to reconcile data from multiple and single sources to determine what's accurate and what can be discarded. It's a fancy way of saying that users can be assured that smart-contract data is accurate and trustworthy. 

As is the case with most digital currencies, investors look to be really excited. However, it's not clear how broad the adoption of this technology will be in the near term.

A Shiba Inu dog posing for a picture.

Image source: Getty Images.

Dogecoin: $7.91 million

Lastly, there's Shiba Inu-based cryptocurrency Dogecoin (DOGE 4.38%), which has been far and away the top-performing asset over the trailing two years. A $50,000 investment in Dogecoin 24 months ago would be worth $7.91 million today, which equates to a 15,720% return. That's a return 31-fold higher than Bitcoin's over the same time frame.

Dogecoin's massive gains have come on the heels of support from Tesla CEO Elon Musk. Musk recently announced that he's been working with Dogecoin's developers to improve the efficiency of the blockchain. He's also proclaimed himself the "Dogefather" and has hyped Doge on Twitter multiple times.

But of all these outperforming investments, none is more dangerous than Dogecoin. That's because its gains have been built on hype, ignorance, and misinformation. Supporters regularly tout its lower transaction fees and growing adoption as reasons to be bullish. Yet look beyond Bitcoin and Ethereum and you'll see that Dogecoin's transaction fees aren't all that low, nor is its network all that efficient. Likewise, the 50,000 transactions it handles daily don't even move the needle next to traditional payment facilitators.

It's also not a particularly popular token with businesses. Only around 1,300 businesses worldwide will accept it as payment -- and it's taken eight years just to get to this level.

With tweets from Elon Musk representing Dogecoin's biggest catalyst, you know you're looking at a pump-and-dump scheme. Despite its massive gains, Dogecoin should be avoided at all costs.