When it comes to comparing Bitcoin and Shitcoins we need to have a look at parameters like scarcity. Only Bitcoin is really scarce, Shitcoins can be launched over and over again, even when a single Shitcoin has a max supply. Bitcoin is limited to only 21M coins and no Shitcoin can be scarcer.
So, in terms of scarcity, Bitcoin is king.

If we are talking about the technicality of scarcity, I do not think Bitcoin is the most scarce among cryptocurrencies. There are lots of shitcoins or altcoins that were released with less than 21m coins. To say some,
Yearn finance (YFI) which is still active today has only 36,666 FYI, there is also this Bomb token with 888 Bombs although this one is only experimental. We can find the list of coins and tokens
here
and see that there are lots that is more scarce than Bitcoin in technical terms. We may agree to disagree but this is a factual information.