In my opinion, Bitcoin is unique because bitcoin cannot be touched, it can only be seen on cellphones, computers and so on.
but bitcoin many believe in its existence and many have proven successful investing in bitcoin.
so bitcoin is a unique digital money.
Bitcoin is unique itself and is the only number cryptocurrency project in the market. There is lot of value holding Bitcoin and those who know this are always making sure they keep holding it so that they will earn more from the market. The existence of Bitcoin had bring about so many cryptocurrency projects to the market making the cryptocurrency market to increase in value and market cap.
BTC is unique because it makes it easy for new wave of currency exchange, it blockchain has a unique wallet address, is not easily comprises to hackers or scammers, it benches on volume of communities members, it's God fatherism to other altcoins. Is transaction made easy and key or password individuals oriented. Bitcoin trades in a every sphere of market.
These features can be prsent too on other altcoin projects and even more advanced. But the only thing that segregate bitcoin to others are the word "decentralized" its the only one proven that can be govern since no one owns it and Satoshi gave that freedom to everyone to use of it. No CEO, no private sales, and whales but early users and buyers are the one considered whales of them but its not due to investment approach but use case of bitcoin instead.
Bitcoin is a decentralized coin just like we have other altcoins that are built to be decentralized like Bitcoin. The market is having consistent adoption and this had been making more people to come into the Crypto market and get some holdings that will make them make there own profits likewise.