My very first thought was: This is a stupid question. But I also learned: There are no stupid question - well, also not quite true

- but questions should be answered respectfully anyway, because often it's just the question was asked wrong, or to be more correct: worded unlucky, often because the asker knows too little of a topic to formulate the question better to be answered more precisely.
So, all what come to me are questions to ask back, to encircle the true point of what this asker actually wants to find out:
What does he understands with 'fame' of an operating system, and why he cares?
If he simply wants to know which BSD has more users I would say FreeBSD.
But every BSD user knows what also the majority of Linux users know:
The only OS chosen by its popularity is Windows

Anything else you chose by what suit your needs best, and not how popular it is.
And since no OS fulfil all needs a lot many run several OSs parallel, not only one.
What's stopping him to do so either?
Which brings us to question to ask more detailed:
What's about Arch what other Linuxes lack, so he compares one Linux distro with all BSDs...

Maybe he simply feels unsatisfied with Arch, or Linux at all for whatever reasons, but at the same time cannot point it out, still lacks of definitions what he actually misses, and is looking for.
Or maybe he still doesn't know yet BSD are not Linux at all.