Atari = Combat 100 hours.
NES = SMB 30 hours.
Genesis = Street Fighter II 80 hours
N64 = Starfox 64 (I could rebuild that game from memory at this point. Probably dropped 1000 hours into it!)
Xbox/PS2/GameCube = Morrowwind 600 hours
360/PS3/Wii = CoD4 800 hours
PS4/XB1/Switch = Xenoblade 2 170 hours

Generation 2 - Adventure (probably), but I also played H.E.R.O. a lot.

Generation 3 - The Legend of Zelda and Super Mario Bros. 3 got so much play it's hard to tell.  One of those 2.  There is an off chance it was Final Fantasy 1 or Ultima 4 though, just because RPGs can get played a long time without it feeling as intense as an action game.

Generation 4 - There were several games I played a fair amount, but nothing clearly dominated: Super Mario World, Super Castlevanina, A Link to the Past, Actraiser, Final Fantasy II (4), Shining Force

Generation 5 - Final Fantasy 7, easily

Generation 6 - Final Fantasy X (probably)

Generation 7 - Both New Super Mario Bros and Civilization Revolution got about 500 hours of play.  One of those.

Generation 8 - Hyrule Warriors, easily

Generation 9 - either Breath of the Wild or Puyo Puyo Tetris on the Switch

There are also some PC games that I sunk so much time into that it would put my time into these console games to shame.  Final Fantasy XI would be the biggest one though.  I put thousands of hours into that.

snes street fighter 2
ps1 mgs1 n64 golden eye
ps2 gta sa, need for speed mw
ps3 uncharted 2
ps4 uncharted 4, rdr2

cant remember for nes and atari 2600 before snes

Second Gen: Donkey Kong (Atari XL/XE)
Third Gen: The Legend of Zelda (NES)
Fourth Gen: The Legend of Zelda: A Link to the Past (SNES)
Fifth Gen: Final Fantasy VII (PS1)
Sixth Gen: Final Fantasy X (PS2)
Seventh Gen: Fallout 3 (PS3/360)
Eighth Gen: The Legend of Zelda: Breath of the Wild (Switch)

Nice job.

N64, TLOZ: OoT most played and favorite.
PS1: Favorite and most played: Tony Hawk.
Gamecube: Favorite and most played: TLOZ: WW.
Xbox: Halo 2 most played. Halo favorite.
360: Most played: Halo 3/Gears of War. Favorite: Bioshock.
One: Most played Halo 5. Favorite:Ori
PS4: Most played and favorite TLOU (i only play it on ps4).
Nintendo DS: Most played and favorite: The world ends with you.

Didn't play that much before Xbox360. Gears of War 3 was my most played game.

This gen it's Sea of Thieves.

MSX1 : Pinguin adventure.
Atari 2600 : Track & field.
Nes : Zelda 2 / Defender of the crown.
Master system : Populous.
Super Nes : Romance of the three kingdom 2.
Megadrive : Langrisser/Warsong.
Amiga : Civilization.
N64 : Donkey kong 64.
Saturn : Dragon Force.
Dreamcast : Sakura wars.
Gamecube : Fire emblem path of radiance.
Ps1 : Langrisser 1-4 / FF7.
Ps2 : Romance of the three kingdom 10 / FF10.
Ps3 : Valkyria chronicles.
Ps4. Stellaris.

PC : Crusader kings 2, over 2000h & everquest over 5 years every days.

RPG & strategy games all the ways ^^

Thank you, sir!  Glad everyone is enjoying it and giving some great lists.  :)

PS1: Legend of Dragoon

PS2: Final Fantasy X

PS3: Fallout 3

PS4: Either Fallout 4/GOW/RDR2

3rd - Sonic the Hedgehog (Master System)
4th - probably a combo of Super Mario AllStars (mainly for SMB3), Super Mario World and Yoshi's Island
5th - at the time, probably Goldeneye. However, I've played Super Mario 64 countless times over the years. Also got plenty of mileage from the first two Tomb Raider games as well.
6th - Resident Evil 4 or Sonic Adventure 2. Put well over 100 hours of gameplay into each.
7th - Super Mario Galaxy
8th - Yoshi's Woolly World
9th - The Legend of Zelda: Breath of the Wild