I don't mean this in a objective manner of debating what the actual best year overall for gaming is (2004 btw)
Rather I'm curious from the standpoint of what was YOUR personal favorite year for gaming, a year so monumental in your experiences that you can't help but always come back to it as a reference point
Me personally, I think it was 2017.
Overwatch was at its highest peak and tons of fun, Team Fortress 2 got its first major content update in years, Night in the woods came out and nier automata came out, giving such profound impact to me and emotionally breaking me and allowing me to better reform my own engagement in stories in video games.
Persona 5 was such a monumental hit that basically broke the barrier for rpcs3 to push it into a proper ps3 emulator (and getting to allow me to play the game without paying teehee). Breath of the wild was doing the same for wiiu emulation at the same time too.
Destiny 2 managed to gaslight me into thinking it was a fun game and I was having a good time.
Overall really impactful year to me, I think time honestly stopped making sense to me past it.