No hard numbers here, but probably Medieval 2: Total War.

Every few months I get the urge to play and log more hours doing a few campaigns.

WoW, Grim Dawn, Don't Starve (Together), Stardew Valley, Terraria, Skyrim, Borderlands

Rocket League, by far. 1500 hours or so.

I'm not sure if it's wow or League.

I played League for 10 years but in my adult phase, while wow was mostly while studying so a lot more hours to burn.

KSP

I have a lot of hours of Morrowind and Doom 1&2, as well as Warcraft 2 and Ultima Online, but I dunno the hour count

Probably 2048 which is just a fidgeting toy for me.

Rimworld

Skyrim over 2000 hours easily, 400 some into Assassins Creed Odyssey and Ghost Recon Wildlands; I have no idea how many I put into Vindictus, which is an MMORPG I played for more than a decade. For phone games I’ve probably put the most time into the Kingdom Rush series, best TD out there.

I'm approaching a thousand hours in Elite Dangerous. Quoting myself from a week or two ago:

It’s different to most other games, by not being goal-oriented except for the goals you set for yourself. No main quest line dictating progress. No mandatory tasks. No win condition. Instead, it drops you into a simulation of our entire galaxy roughly 1300 years in the future, where humanity has mastered hyperspace travel and spread through hundreds of star systems.

(To give an idea of the simulation’s scope: Around 85 million systems have been recorded by players so far, and those are a vanishingly small fraction of what’s out there. Space is big.)

I like that it offers a variety of activities to fit whatever mood I might be in on a given day. I can hunt pirates, mine asteroids, engage in a bit of piracy myself, find and collect bio samples, infiltrate rival settlements, venture into vast unexplored areas of space, discover Earth-like worlds that nobody has ever encountered before, defend humanity against hostile forces, photograph beautiful stellar phenomena, rescue stranded survivors, customize and finely tune my ship to perform beyond its original specs, team up with friends, pledge to a political power and expand their influence, or chill out as a space trucker and haul cargo to earn enough money for my next upgrade. It can occupy all my attention, or just be relaxing entertainment while I listen to music or an audiobook.

It’s an MMO in the sense of having a large game world (galaxy) shared by all players in real time, but PvP is optional. One mode exposes you to other players, while another limits you to NPC encounters. You can switch between them at will.

One warning: A space ship has more than a few controls to learn, and they’re better suited to a game controller or HOTAS than a keyboard and mouse. I use button combinations for almost everything beyond basic flight controls, since there aren’t enough buttons on a controller for everything.

Team Fortress 2 easily. Been playing since 2008. It scratches an itch that no other game can scratch. Ironically though, my second favorite fps game is also TF2 (Titan fall 2)

That I know of (3000+): Team Fortress 2

Probably(500+): Super Mario 3, or Apotris

Old School RuneScape, Gran Turismo 5 & 7, The Crew 1, 2 & Motorfest and I think Midtown Madness 1 & 2 are also high on my list of most played games.

DayZ, I have around 3000 hours in it.

WoW, CS 1.6, Warframe, and ARK

I think something like 5k hours into Warframe, 15 years into WoW (at least 2 of my characters have 1+ year of playtime--so 17k hours just on those 2; and I max-leveled every class of character up until Battle for Azeroth) and so far, 2 years into ARK. Just over 3.5k hours of playtime between ASE and ASA.

Arma 3

Sadly as I get older I game less hours, so most of my games on this list are older. LoL, wow, Dota 2, modern warfare 2 (2009), Wingspan(online boardgame), PubG battlegrounds, counter strike 2, terraria. I haven't played fps, wow, or dota for years, but they still dominate this list. It's funny because if I made a list of my favorite games, it would include almost none of these, except terraria.

World of Warcraft is the absolute winner in my case. I have no idea on actual numbers, given 99% of my time was in private servers, with a very brief stint on official. Only one of those private servers is still around, with my character from Warlords of Draenor times still there.

Outside that, probably Skyrim (many hours playing pirate versions, modding it with more lethal combat, more lore-friendly armors and "actual" civil war, among other things). I wonder how many hours I've spent on Dwarf Fortress, as I've only played the freeware version, starting with 0.34, before trees had height.

I'm a bit ashamed of it, but Overwatch, I really enjoyed the multiplayer and played with some cool people I met in game. Stopped playing when OW2 released.

My second most played game is Destiny 2.

Maybe something is wrong with me...

When I played on PC more EverQuest, counterstrike, TF2, wow, Skyrim

After playing more on console ff14, elder scrolls online, pillars of eternity 1/2, and souls games (ds2, ds3, bloodborne, elden Ring)

I also like to play Indies and smaller games but those are the ones I keep going back to

Braben & Bells "Elite". The original one on the C64.

DotA2 and possible WoW next.

Stardew Valley and Core Keeper ;)

Probably still World of Warcraft. When I quite around 2010, I had close to 700 days /played time on my main, and another 400 days between various alts.

I have few hundred hours in Minecraft. And probably something like 180h in Witcher 3 GOTY. Recently I 100% Yakuza 5 with 120h on the counter, and it was (mostly) fun, because game is packed with many different minigames, so it wasn't repetetive.

My top four on steam are:

• Garry's mod - 2800 hours
• CS:GO (CS2 now) - 2100 hours
• Terraria - 1000 hours
• Team Fortress 2 - 555 hours

In no particular order:

• Ragnarok online
• Darkspace
• Monster hunter (multiple games)
• Dj max (multiple games)
• Garry's Mod
• Aliens VS predators 2 (1998)
• Halo
• Warframe Phantasy star online (and 2) Path of Exile Morrowind probably.

I put the most hours into Awesomenauts during college... really miss games that time

7 Days to die. 1600 hrs on steam Call of Duty. 1200 hrs on steam

The most that I have proof of is Europa Universalis IV at a little over 1k hours, but I wouldn't be surprised if my time on Guitar Hero 3 in high school surpassed that by quite a bit. I played a lot of Guitar Hero in high school...

The Binding of Isaac

steam says I played Fallout 4 for 436 hours, but that seems very high. not sure if that count is accurate.

Probably counterstrike back in the day, possibly battlefield 2 including the Project Reality mod. That was back when gametime wasn't really tracked and I had a lot more spare time Possibly WoW, but I only played for a couple of years or less and for a few hours a day at most.

Currently my highest is Forza Horison 5 with like 1200 hours. Have a few others with 500+ hours although a few are inflated at least 100+ hours because the game locked up on closing and counted as played for several days multiple times.

According to Steam the top 3 are:

1. Oxygen not included
2. Civilization 5
3. Factorio

But that of course does not include the games not running from Steam and pre-Steam games. So World of Warcraft is somewhere in there too. And the final Top 1 must be Transport Tycoon Deluxe (even if you don't include OpenTTD).

As much as Monster Hunter is my favorite series of all time, and I have about 1600 hours combined total over several games, it's still not caught up to my total of over 2000 hours in Warframe. Love that game to bits but yeah I think I played it enough.

Most other games I play, that I played a lot, hover between 100 and 300 hours each.

Elite, the original one, on Commodore 64.

Guild Wars 2 has been my theme park MMORPG of choice on and off for the last 12 years, with >2500h. I have also spent ~1000h on Elite Dangerous.

Persona 5 Royal

150 hrs and I'm almost done with it

Maplestory and Warcraft 3 almost certainly hold the first two places from an age gone by, but I don't have numbers for those.

For games that I do have numbers for, Anno 1800, Stardew, and Total War Warhammer (especially if you combine the trilogy).