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.*