Most hours spent on one game?

Over 200 hours in Half-Life. It is my annual play through. Haven't missed year since it came out.

Sims 4 I have over 225 hours

However total I would say Persona 3 FES or GTA San Andreas. Most time I spent playing in one sitting was House Party. I spent over 24 hours playing. I was having too much fun and it was 36 hours later before I said "wait the sun is out....what day is this?"

World of Warcraft.. Ragnarok online.. and Earthbound too.

I have at least a couple thousand of hours in r6 siege and csgo each.. and a thouand of hour in GTA... tho i don't play any of them in a regular basis anymore

Spent a little more than 2 thousand hours on CS 1.6, 500h on CS:CZ
Around 1 thousand on CS:S and now 2 thousand on CS:GO.

Spent at least the same on Ragnarok at the past.

Too many too count i think alone in Arma more then 1000+ Hours

SCP secret laboratory 859 hours but in csgo I have 673 hours

Almost 10k hours in gmod! Also over 5k hours in ARK

ive spent 3000+ hours on gmod and coming up on 700 hours on Rock league!

Me it's GTA V RP I spent 3k hours