IMO as long as you can buy certain ordinary things with an altcoin they can be considered money too. It's just bitcoin have wider adoption than any altcoin so it can be considered superior (in terms of adoption, other things can still be debated).
It's not really just that they are more widely adopted, it is that it is more well known (which really isn't that well known to begin with). Cryptocurrencies are still a mystery to a lot of people, but some people can remember the "scary" things about it, and that it is associated with criminalized hackers and the spooky dark web...
I mean the whole silk road scandal happened not that long ago... But it is forever in crypto years since it is such a new phenomenon.