favorite phono cartridge

zyx UNIverse. I am on the second iteration after many years with the first. Fits my style in musical taste and system very well.

Seems most folks like best the cartridge they own and use in the here and now. Not surprising. I vote with Altanpsx's principle: this is an entirely subjective question and system-dependent discussion. However, a ZYX UNIverse low output version might be my favorite, if I owned one.

Of course it's a question of personal taste, but since that's what the OP asked for, my choice would be (and is) ZYX UNIverse II-X-SB, low output.

I agree, there can be no definitive "best". There can be only a consensus "best". There certainly can be an individual's "best". "Best" is always a moving target. Quite often there are new bests. Positively subjective. Having said that, a "best" that is determined by design, material, workmanship, imagination, functionality and/or a true step forward, a revolutionary change, are at least one of the very "best". This is true no matter the system, environment, taste or other personnel feelings. Yes "best" is subjective. But all great(best) things like art, music, poetry, novels and yes audio equipment are arrive through time and consensus.
I have not heard every cart(ZYX) out there but from what I have heard,
mine are;
MC type
Lyra atlas
Ortofon anna
Dynavector DRT XV-1s
Clearaudio goldfinger
Benz Micro LPs

MM type
Grace f9 / soundsmith Ruby OCL stylus

*I have heard several other cartridges that do not make it on my list.*

Ortofon A-90 still hangin in there.