So in other words it is completely subjective and cannot be quantified through data? So why are so many people clinging to GOTY nominations and MC scores?
Yes a game can have very different reactions from two people playing them. I keep bringing up TLOU2 because it's a perfect example of how there is no universal standard for measuring a "best game" if we're taking your definition into account. For as many people loved it, I literally saw many others expressing strong negative reactions as they played it, live.
For some reason there's a very vocal minority of TLOU2 fanbase who want to pretend every person who didn't like the game is just either anti-Sony/anti-PlayStation or has an agenda against LGBTQIA+ people. While I'm sure for some bigots that's the case, you also have to be realistic and acknowledge some people have legitimate reasons for not thinking it's such a "best game", and that's okay.
I mean by your definition, many people would put something like Halo 3 (the MP) as their "best game", or Valorant, or R6 Seige, or Street Fighter V, or Mario 64, or Sonic, maybe even some super-obscure game you may not have even heard of. I'm not 100% sure using a solely subjective measurement is any better than a solely objective (i.e data-driven) measurement. You need a good mix and even that will not be 50/50 as it will depend many times on the game itself, and you need to also take into consideration its relevance at time of release and how it plays today.
Also I think you guys vastly overrate Nintendo's ability to move hardware with their own software. That has never really been the case. NES and SNES were strongly driven by 3P support. The N64, especially in the West, was driven strongly by 2P support (Rare) and 3P support (games like Turok, Quake, DOOM etc). Gamecube benefited a lot from select 3P support from companies like SEGA.
If you want to test that theory of yours and see why it's wrong look no further than the Wii U. Almost single-handedly propped up by Nintendo 1P yet that system never got past 15 million LTD. Just goes to show it doesn't matter how good the games are; if the hardware is unappealing, features/services bare-bones and you don't have some decent 3P support, you will always struggle to keep relevant.