Despite the fact that most of us play hundreds of games during each generation's lifespan (or at least many, many dozens) there's arguably one single title that you spent playing more than the others.  This thread isn't asking for your favorite game of that generation, or the one you liked to play the most.  Just what you believe your most played game would have been if, like modern consoles, it had kept track. 

So what was it for you for each one?  And do you notice any trends in your gaming habits by your list?  

I'm pretty sure it's Smash for every system since the Gamecube.

NES - Most played: Super Mario Bros.
Favourite: The Legend of Zelda

SNES - Most played: Super Mario World
Favourite: The Legend of Zelda ALTTP

N64 - Most played and Favourite: The Legend of Zelda OOT

Gamecube - Most played: Super Smash Bros. Melee
Favourite: The Legend of Zelda TP

Wii- Most played: Super Smash Bros. Brawl
Favourite: Super Mario G2

Wii U - Most Played: Hyrule Warriors
Favourite: Donkey Kong Country TF

Switch - Most Played: Xenoblade Chronicles 2
Favourite: Xenoblade Chronicles 2 and Super Mario Odyssey

Gameboy - Most Played: Pokemon Red
Favourite: The Legend of Zelda LA

GBA - Most played and favourite: Mega Man Zero

DS - Most played and favourite: Mega Man Zero Collection

3DS - Most played: Stella Glow
Favourite: The Legend of Zelda ALBW

I replayed Gothic 3 a lot. So my wild guess would be:

Gen 6: Gothic 3
Gen 7: Gothic 3
Gen 8: Rocket League

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.

PS1/N64: Chrono Cross and Ocarina of time.

PS2: Spyro Eternal Night and Shadow of the Colossus (multiple playthoughs).

PS3/Wii: The Last of Us and Rune Factory Frontier.

PS4/Switch: Persona 5 and Breath of the Wild.

I only play games that have a beginning and an end, so they would have to be games that simply take a lot of time to finish. I like to explore everything and play all the DLC as well. Some RPG's can take me a month to finish and 100-130 hours in game time. I think Fallout games have been real time sinks. Some western RPG's as well, the ones that start out on the PC.

Since Dreamcast gen: Marvel Vs Capcom 2.

Until today, I’m still playing it

PS1 - Crash Team Racing
PS2 - SSX Tricky or Wipeout Fusion or Ratchet & Clank 2 or Rayman 3
PS3 - GTA IV or Mass Effect or LittleBigPlanet
PS4 - Witcher 3, Closely followed by Persona 5 and Rocket League.

PSP - Wipeout Pulse
Vita - Rayman Legends

Gamecube - Mario Kart Double Dash
Wii - Mario Kart Wii
WiiU - Mario Kart 8
Switch - Mario Kart 8 Deluxe

GB - Super Mario Land 2
GBA - Pokemon Fire Red
DS - Mario Kart DS
3DS - Mario Kart 7

Xbox - Star Wars Knights of the Old Republic
360 - Absolutely No Idea. 
XBO - Forza Horizon 4

Trend: Mario Kart

Hard to remember or tell maybe. Not like nowadays where it records your time.

Pre-consoles - Moonquake for the Acorn, Premier Mananger for it as well.
SNES - Mario Kart or Killer Instinct maybe.
PS - FF7 or 8.
PS2 - KH2 probably, but around here I played Championship Manager 01-02 loads, even into 04-05 as I got updates to the database and did custom ones (was at uni so had no money to buy games).
PS3 - Black Ops or Tekken 6
PS4 - This one's recorded, it's Overwatch, then Dragon Age Inquisition (both over 500 hours).