I think 1998 takes it for me.

It does not include my favorite games in any category, but the games released this year had such an impact on gaming as a whole.
Ocarina of time, Half-Life, Starcraft and Metal Gear solid all where defining for their genres.
Even if Pokémon originally released in 1996, the first western release of the series was in 1998 marking the year it took over the world.
Tekken 3, my favorite non-smash fighting game left the arcade and entered our homes in 1998 as well.

Pretty much the only thing missing from 1998 is a major console release.

2017, though 2020 can maybe overtake it since I haven't played FF7 Remake or Ghost of Tsushima yet and I already consider 2020 the second best year of gaming. 2023 is another candidate but I haven't quite played enough games for the year to rank it yet. My top 10 years:

1. 2017 (DDLC, BotW, Odyssey, Automata, Samus Returns, Horizon, Dragon Quest XI, Hollow Knight)
2. 2020 (Black Mesa, OMORI, Will of the Wisps, Doom Eternal, Hades, Last of Us Part II, Cyberpunk 2077)
3. 2018 (SSBU, God of War, Celeste, Marvel's Spider-Man, Deltarune Chapter 1)
4. 2013 (The Stanley Parable, The Last of Us, Revengeance, Bioshock Infinite, GTA V)
5. 2011 (Portal 2, Skyrim, Skyward Sword, The Witcher 2, Tales of Xillia)
6. 2012 (Diablo III, Xillia 2, Borderlands 2, Virtue's Last Reward)
7. 2004 (Half-Life 2, World of Warcraft, Twin Snakes, Snake Eater)
8. 2008 (Vesperia, Brawl, Persona 4)
9. 2015 (The Witcher 3, Undertale, The Beginner's Guide)
10. 1998 (Half-Life, Ocarina of Time, StarCraft)

2002 for me. Metroid Prime, Zelda Windwaker, Mario Sunshine all in the 1 year. How often have nintendo released a mainline game for all 3 franchises in the 1 year.

2001 was definitely the best year ever for an individual platform (PS2), and probably also the best overall. It was a magnificent year in all aspects. New genres, generation definers, generational wow factor, GTA3, Halo, incredible diversity of great games, Gamecube and Xbox launch, you name it!

2020 for me without a doubt.

Cyberpunk 2077
The Last of us Part 2
Ghost of Tsushima
Nioh 2
Demon Soul Remake. 

2001. Halo CE is in the convo for my top game of all time. Then you have GTA3 and Civ3, both genre defining games.

There are lots of other good years. But, 2001 is *the* year

2014. Funnily enough, the so called "worst Nintendo console" gave me my best year in gaming. Bayonetta 2, DKC Tropical Freeze, Mario Kart 8, Super Smash Bros. for Wii U, Captain Toad, Shovel Knight, Hyrule Warriors, The Swapper...

And 3DS also had a killer year for me. Pokémon Omega Ruby, Theatrhythm Final Fantasy CC, Professor Layton and the Azran Legacy, Kirby Triple Deluxe...

I think I'm not lying if I say 2014 was the year I played the most in my life xD

One could argue that 2023 is also one of the best years with:
- BG 3
- Zelda TOTK
- Spiderman 2
- RE4 remake (in VR)
- Alan Wake 2
- FFXVI
- Starfield
- Diablo V

I'm tempted to just give it to 1991 - plenty of reason for that - but my subjective bersonal top is 1990.

1998.

Easily and without a doubt. That year was right in the middle of the Golden Age. My list of favourites has plenty of games from this era, and from 1998 itself. Even outside that list, there’s a lot more great 1998 games. My top 10 has two 1998 games, including the all-time greatest. It’s funny that from the list of winners in OP, from the 1998 list I only played one game in spite of that. Including big names like those as well only solidifies a 1998 win.