In a year I had over 200 DAYS played on World of Warcraft back in 2005-2006. That's over 13 hours a day, then I quit abruptly and later tried a couple of expansions casually.

Second is probably Counter-Strike 1.#. No idea actual playing time but would estimate around 1000 hours.

The above two I don't regret spending my time in. Made a lot of friends and it all felt rewarding.

Then there are games like Civilization VI (~200 hours), Rimworld (~300 hours), Tropico (~200 hours) and even Path of Exile (~500 hours). These games are not really rewarding, other than little dopamine hits that gets you continuing playing forever.

Edit: Added hours!