For me it's Destiny 2. Here is a screenshot of my "Time Wasted on Destiny"! 4501hrs I've spent playing..... Let's see yours?
For my Current Steam account, it's Gunfire reborn at 967.2 hours. However, I do have an older account I used for trading that has over 2k hours in TF2.
Borderlands 2: 770.7 hours
CSGO, TF2, Terraria in that order. Can't really estimate the times for the first two since idling, but Terraria I have 500 honest hours.
Wow!
For single player game, I just set new high with 176 hours in WH40k:Rogue Trader, and it will increase when DLC releases.
For multiplayer MMO, not going to look 🙂 but it's not close to those numbers.
I don't have records for that unfortunately.... still have plenty of games the old way and not on steam.
Even today, I have some games on steam because they were a either a gift or purchased at 1€, but I rather play my original version, that's why I still keep a DVD player.
So... If a number is to be thrown into the wild.
I played DOOM 2 During 1994 to 2010 I would be playing an average of at least 1h a day, every single day. Some days lots of hours, school/work days, less. That would account for the very minimum of 5840 hours, probably the real number is substantially higher.
On Steam the best I have is 189 hours on Nier Automata.
Now I'm gonna head to Half Life to kill some nostalgia.
EDIT: forgot to say the actual game with most hours lol
I spent around 4000 hours in The Elder Scrolls online, between Xbox One and PC. This was before Greymoor.
Four thousand hours?
I would have to get Xbox live to check the hours in game I have, but yes. 4000 is on the low end of the time I put into the game. I stopped shortly before they did a bunch of overhauls to the game that I just didn't agree with. Now all my gear sets are useless in the PVP arenas. It's probably fine for the people who stuck with the game, but they nerfed specifically proc sets. I used to only wear proc sets. That was kind of what I grinded so hard to get, so I took is as a big "kick rocks" from the devs.
For me it's Melvor Idle. But that doesn't count I guess since it's an idle game I was running in background while doing other stuff. So this is what my top12 looks like on Steam:
Of course that doesn't account for stuff I played on GOG and elsewhere but I doubt any of it would have much more hours spent on.
EDIT: I remembered I used to play Hearthstone for 3 years (on and off, but still). No idea how many hours but probably at least 1000
Currently, I have 1,646.5 hrs in Valheim.
Back prior to MMORPGs, I spent a lot of time on various Circle MUD derivatives. Darkover would probably be my all time high.