Open your Steam library. Sort by “Hours played.”
What are your top 3 games?
Mine are:
Fishing: North Atlantic 317.7 hours
American Truck Simulator 186.3 hours
Project Zomboid 156.3 hours
I only have two games in my Steam library as of now, but mine are:
Sonic Mania: 65.4 hours
DELTARUNE (Chapter 1 & 2 DEMO): 6.4 hours
Yeeeah, I’m much more of a console gamer, LOL.
Likely not completely accurate due to losing my gaming history at least once while migrating computers but…
Fallout 4 2,600 hrs on record
RimWorld 2,224 hrs on record
Starbound 1,073 hrs on record
Total War: Warhammer 2
XCOM: Enemy Unknown
Civilization V
Stellaris (where my avatar is from) is in number 4.
Total War: Warhammer 1 is down in slot 9. TWWH3 releases in a couple weeks; since these games have combined maps where you can play prior game factions in the new game, that means I’ll likely never launch WH2 again. Now that I have a baby, it will likely be a very long time before WH3 catches up to WH2 regardless…
Oxygen Not Included: 968 hrs
Kerbal Space Program: 837 hrs
Factorio: 561 hrs
Oh man, that’d likely be in my top 3 if I didn’t play it for years and years off of steam before finally getting it just a couple years back when I was mostly over it. Also when I do play it I launch it through CKAN so Steam doesn’t see it at all
Stardew Valley: 485.9 hours
Terraria: 437.1 hours
Streets of Rogue: 355.2 hours
All three of these benefit from the fact that a college friend and I stay in touch by gaming together one night a week, and all three are games we’ve used for that purpose (our current game, Age of Empires II, is tenth place at 70.6 hours).
In a near fourth place, though, is Baldur’s Gate at 334 hours, but that’s not counting all the time I spent on that game back when it was new, before Steam even existed. If I were to somehow find how much time I spent on it then, it would certainly move up into my top three, and possibly my #1.
Mad Max 49 hrs
Shadow of Mordor 41 hrs
Elite Dangerous 34 hrs
I beat the first 2 games so that’s no surprise. But I barely started Elite Dangerous; it was too frustrating and every mission was a failure so I gave up quickly. I don’t know how there is 34 hours in that, it should be more like 4 hours.
Black Desert Online - 621 Hours*
Fallout 4 - 353 Hours
Ark: Survival Evolved - 343 Hours
Dragon Age: Origins - 329 Hours
I’m giving Black Desert Online an asterisk because the vast majority of that time wasn’t spent actually playing. The game is a grindfest and actually designed so you start your character doing some task (fishing, riding a horse in a big circle, etc) then run it in the background with minimal resource impact while your character skills up (or collects expensive fish, trains their horse level, etc). I’d guess that I had less than a hundred hours of actual keyboard time with BDO, the rest was idling while I was at work or otherwise doing other stuff.
Dota 2 - 724 hours
Rimworld - 372 hours
Star Trek Online - 147 hours
I’m a bit surprised, really. The last time I played Dota was in 2014. The last time I played STO was 2013. I’d have thought some other games would’ve risen to the top but I guess my attention span ain’t what it used to be.
Note - probably about 100 hours of Fallout 4 or so being false positives (left game on but tabbed out happened quite a few times) but otherwise probably accurate
Fallout 4 - 1997 hours
Fallout NV - 646 hours
Skyrim (SE + OG) - 587
Fallout 4 had vanilla, survival, and heavy modded versions, so, lots of different iterations there.
War Thunder 1323 hours
Company of Heroes 1253 hours
Rocket League 761 hours
Company of heroes gets up to 1556 hours if you combine the “legacy edition” and the new steam version that they released which switched the multiplayer from an old abandoned system to steam. They’re tracked separately but are the same game.
I think steam started tracking hours played in 2009, so if you played games before then their hours won’t count towards this. Or if you played it anywhere but steam, obviously.
Yeah, I’d be surprised if The Division, The Division 2 or Red Dead Online wasn’t in one of my top three slots overall but those were through Uplay and Epic/Rockstar, not Steam.
Edit: 872hrs in Division, 1,472hrs in Div 2 per Ubi Connect. Stick that in your pipe and smoke it, Black Desert Online!
This thread reminds me of how comparatively little time I have anymore to play games. 
Adulting sucks.
Still, I like having money, a good house, a family, and all that crap. I’m happier than I was when I was poor, alone, living in a tiny apartment hunched over a keyboard for hours and hours living a virtual life. So I shouldn’t whine.
But the gamer in me is not satisfied.
I’ve got about six that are so close it hardly makes sense to list three. Two are tied for 3rd presently.
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Fallout 4 - 2,128 hours. I’d have played this more if the mods I used didn’t mess up my game. . .a few times.
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The Elder Scrolls Online - 897 hours. I haven’t played in over a year, but I still haven’t played through all the content.
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Fallout 76 - 552 hours. I’m still playing this, and will likely pull ahead for sole posession of 3rd place tonight.
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The Secret World: Legends - 552 hours. A great MMO based on the spooky side of legends, like Lovecraftian horror, werewolves, vampires, etc. If it weren’t buggy, and they didn’t totally revamp the magic system and erase everyone’s gear in the process, I’d probably have played it more.
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No Man’s Sky - 548 hours. I bought it a couple years after launch. It’s a bit. . .empty. You pretty much have to find your own goals. I found a cool, beautiful Earth-like planet and that must have been mine, because I lost interest afterwards. I’d be interested in a sequel if they worked on the ‘game’ part of the game.
Honorable Mention:The Elder Scrolls V:Skyrim - 478 hours. I include this because, like Fallout 4, I’d have a lot more time in-game if the mods I used hadn’t ruined my game - multiple times. I know, I’m a slow learner, but you have to understand - the mods are really, really fantastic. 
They bring a older game up to modern graphic expectations (they look beautiful), add content, add interesting, entertaining and HELPFUL companions (Inigo). If I could play a stable, modded version now, I’d put another 400 hours in.
I’d probably have lots of hours in this but I don’t play through Steam. I play a bit every day at least for years. I’m a Grand Master (one of the lifetime subscription folks from before release of the original game) and got more than my money’s worth!
I truly enjoyed the game, but it got to the point where fully half of the quests were bugged. Really disheartening to do all the work and not get the reward. Also, two of the quest areas were desert, which was at least one too many in my mind. . .but the New England town with the Lovecraft theme was just wonderful. I want more of that.
I mentioned this in another Fallout 4 Thread, but if you ever play it again, try the mod Huntress Manor for a Dunwich Horror tie in for Lovecraftian horror.
You’re evil. . . EEEEE-VIL! Tempting me back to FO4 with Lovecraft mods, when you know mods have been my undoing time and time again.
EEEEE-vil.
(hits reply, does google search on “huntress manor nexus”)
XCOM - 1,115.4 h
Dragon Age: Origins - 480.4 h
XCOM 2 - 472.8 h
XCOM 2 may be skewed by how slow the load times are for me, so I’ll throw in:
Crusader Kings II - 417.8 h