If you are asking in terms of returns that Bitcoin has given us since the start, it is tough to find such a coin now. Because at that time there were a few people in cryptos and with adoption and hence, demand price pumped up. But you can still expect better returns than traditional investment assets like shares, stocks, property and gold. They are relatively stable market than cryptos and hence, don't give high ROI. But in cryptos it is pretty much possible but there is more risk. That is why it is called investment for millennial.