NES: Mario 3 Maybe? Bubble Bobble? (yes seriously lol)
GB: Definitely Pokemon
SNES: Probably DKC2, slight chance of Mario RPG, Secret of Mana, or Mario World
N64: Mario Kart 64
GC/DC: Tough one actually.. This is an odd gen for me as this was the height of shopping around and just buying & spending lots of time all sorts of shit by Nintendo & their third parties, and didn't really get too into the mainline Mario or Zelda games. Probably Smash melee, but Eternal Darkness or Tales of Symphonia could be close. Was also playing Everquest hardcore w/my friends at this time.
Wii/DS/360: Definitely Gears of War and it's not even close lol
Switch/XB One: Easily Overwatch. I have more hours logged with my main D.Va (close to 100) than my most played Switch game Zelda (which stands at like 85) lol
Don't know if/where you'd throw PC in there but Minecraft, Starcraft, Everquest, and Roller Coaster Tycoon have to be 4 of my most played games of all time.
"We hold these truths t-be self-ful evident. All men and women created by the.. Go-you know the.. you know the thing!" - Joe Biden