PS1: Spyro
PS2: Nothing special about it but I automatically think of the Euro 2004 game for whatever reason... FIFA was its most enjoyable before online happened
other than that, GTA Vice City.
PS3: Mass Effect 2 or Batman: Arkham Asylum
PS4: Fallout 4 probably. GTA V took up a lot of my life, though, and Fortnite looks set to do the same.