I’m thinking 2015 - Witcher 3, Undertale, and Kerbal Space Program are all classics. Fallout 4, Arkham Knight, and Cities Skylines were all excellent too, though fallout 4 and Arkham knight aren’t necessarily the best games in their respective series.
One could argue Tetris could carry the whole competition alone, but it is joined by Mario Brothers, Duck Hunt, Spy Hunter, and Gauntlet in 1985
I would leave it at that, except Pac-Man, Frogger, Galaga, Defender, and Donkey Kong make 1981 a contender