Minecraft. I spent a lot of time on it, especially when playing with friends on my server.

Because I've been playing on and off for around decade - if not a little longer - on xbox360, I'm going to say Borderlands.

I still have a ton of content left in the game since I only had the zombie island and underdome riot DLCs until three years ago and even then still had only really focused heavily on my main account for most everything in game, leaving my playthroughs with the others far behind in the dust.

This depends on what you define as in game. According to Steam, I've spent the most time on NGU Idle at 3306 hours, but a large amount of that was spent with the game running while I was asleep or at work. For Steam games with the most hours, I've spent 840 playing Path of Exile but that doesn't include the 200 or so hours playing the standalone client. This is followed up by 440 hours playing Terraria (which doesn't include console version hours), and Realm of the Mad God which I have 325 hours playing.

If we include MMOs in the mix, I've easily clocked 1500 hours playing both World of Warcraft (between Classic and Retail up to and including Mists of Pandaria) and Guild Wars 2 over the years.

Funny enough, I wouldn't include any of these games in a list of my favorite games other then Terraria, so that's good to keep in mind :)

Kerbal Space Program (not 2) has around 300 hours on my steam account. I have played around equally much on another account. KSP2 is painful to see perform so badly.

Toram Online, 700+ hours. Not counting the time spent on the PC port though.

I dont know exactly but I have around 300 hours in every soulsborne game inkluding elden ring. Such good times.

Monster Hunter

CSGO.

According to Steam, it is Stellaris with over 1,000 hours.

I’ve yet to come close to my record of 800+ hours in Rust with any other game.

Any of the Championship Manager games.

Evil Dead: The Game. 3k hours in the past year and still my daily goto. Probably the most underrated game of all time.

Workers and Resources: Soviet Republic. 189 hours attempting to create a sustainable, green powered, communist utopia.

not really a single game but probably accumulated the most hours playing Super Mario World kaizo romhacks

single game would probably be Battlefield 4 though

Guildwars2, 14000+ hours. Mostly WvW.

Either quake 1 as a kid (netquake CA)… RTCW as a teen, or world of Warcraft as a growing adult.

Arma 3 and that is mostly "Escape From" as it's an easy drop in game mode. Although I think I still have way more hours in Europa Universalis 4 but that isn't counted for... reasons.

Also I swear my hours used to be way bigger years ago. I am not crazy right? Like only 170+ hours in TF2 I have definitely played that way more.

On Steam it's Phantasy Star Online 2 (which I am no longer actively playing.)

Throughout my life it's probably Sonic Robo Blast 2 (a fangame.)

Mass Effect Trilogy. Each game when I initially played had 3-4 careers of 50 hours. This was when one game’s choices affecting another game to this degree was very new so I would be trying many different permutations.

Definitely the case if we include LE later on.

4000 hours in the Sims, Sims2, Sims3 and 4. Around 8000 in WoW Retail and around 2000 in RimWorld.

Mario Kart.

First Chivalry game was dope. Funniest pvp hack n slash ever. Can't even get mad when you die cuz the voice acting and emotes n shit was over the top hilarious. Imagine if "Were knights of the round table" from Monty python was a medieval call of duty that was it.

Chiv 2 is pretty good too but didn't get too deep honestly cuz I sunk in hundreds of hours on the first and retired.

I had over 10,000 hours of Call of Duty 2 (2005 version). 4000 hours of the first Call of Duty Modern warfare and currently have 3600 hours of Csgo. It’s common to run into 6-8000 hour accounts in Csgo.

Anything less than 1000 hours in Csgo is considered new to the game still.

Minecraft. I don't know how many hours, but I bought it before nether portals were a thing and I've been playing it ever since. Sometimes a game just clicks for you.