Scarcity in itself doesn't create value though. You can have as little supply as you want, but if there is no demand, there won't be any value.
I'd argue that the thing that gives Bitcoin value is its brand name, its first mover advantage. Everyone has heard of Bitcoin, but almost no one has heard of, say, Ethereum or any other altcoin.
Compare Bitcoin to the thousands of shitcoins that are also scarce and have limited supply, but are worth (almost) nothing because they have no brand name. It's not that they are technically worse than Bitcoin, some may even be better than Bitcoin with some cool features. Yet they aren't more valuable than it. Simply because Bitcoin was the first.