There are thousand of token but every token does not exists as a beneficial token and many of them disappears after a short period of time. I think here unique refer to the qualities that one coin have and due to such qualities bitcoin remains the top priority of every individual.
Lots of coins proved to be successful but not a single coin can ever be more successful than bitcoin. It is a decentralized asset and its success is prominent whereas other coins must possess some sort of doubt so I think we have to choose a unique project like Bitcoin.
No not " every " because some tokens are still good. If there is one unique feature BTC have, I think that would be decentralization. There are other coins who claim they are decentralized but it's not really believable.
Another reason on why BTC became more successful is because it is the first crypto that is invented. If you lack in knowledge, definitely BTC is the coin to go or to start but as long as you gain more knowledge, that is the time to add other cryptos because like I said earlier there are still other tokens or altcoins that are good. A newbie can even post a thread here like other newbies to know some of them, if they want to start with more than one coin on their wallet.