Very tough every generation has had some standout moments for me at least, just a few off the top of head….
Speccy128k +2 - was my first real computer and having access to hundreds of games/arcade conversions for a reasonable price was quite something.
Megadrive - Sonic, Streets of Rage, Revenge of Shinobi and the countless SHMUP’s
SNES - Super Mario World (my first Mario true love). Also Zelda, MarioKart, Castlevania, Metroid to name but a few.
N64 - Mario 64, both Zelda’s and Goldeneye!
PS1 - Final Fantasy VII, ploughed 100’s of hours into this!
GameCube - Mario Sunshine, Zelda and RE4.
For now though I will go with 4th gen.