Steam

Tough question. I'd say Stellaris and Neverwinter Nights.

Stellaris is giant with so many options, it would take a while to get stale.

Neverwinter Nights has hundreds of homebrew campaigns available, and with the PRC mod also hundreds of classes & races to play.

Quake Champions and Monster Hunter Rise

siege and tekken 8

Civilization 5 and Space Engineers

Killing floor and chivalry. It'd be like Valhalla.

CS2 & super auto pets

Apex and Rimworld

Dota and Baldur's Gate 3.

I've been playing Dota since it was a Warcraft 3 map...

And Baldur's Gate 3, I don't know if I've ever done a second playthrough of any RPG I've ever owned before. Most of them I usually get bored and quit before the end because it's like... I get it... But Boulder Gate 3 I've beaten three times so far currently working on a fourth run which is an honor run. And I've been making a list of mods that I want to try to make.

Rain World!!!!!
Second place is hard to do though! Oxygen Not Included, I guess?

Path of Exile for sure, not sure about the second though. Maybe Dark Souls 2, Elden Ring, or maybe XCom 2.

Satisfactory and Titan Quest

Would choose those 2 because it would let me kinda bypass that limit
Source Sdk 2013 Multiplayer
S&box

Just woke up. I thought this was a picture of valheim with a deathsquito on the background. Which is interesting because I was probably going to have to pick Valheim and Sims 4. If I can only playb2 games forever I need sometimes that doesn't necessarily have a main quest then it's done and both of those fit that.

Valheim and Starfield.

No Man's Sky and Light No Fire

That is a hard choice

Stellaris is number one and Skyrim or Fallout 4 for number to just based off mods available.

… what is steam? 👀