What are some of your favorite "older" games available on steam?

There's been a lot of talk lately about newly released games feeling unfinished or lackluster, which I agree. I've been buying a lot of new games lately only to realize that they probably need another 6 months or year to get finished. I'm relatively new to gaming, so I'm wondering what are some of y'alls favorite games from the past 10, 15, 20 years? Specifically looking for steam games as I only play on my deck