Probably RimWorld. Somehow I've managed to accumulate nearly 4,000 hours. I'm pretty sure I could play for another 4,000 easily and then for the rest of my life. I love the stories that come out of each colony and how attached I get to pawns. I'll never forget Dinkleberg, the troublesome cat that has nearly wiped my colony twice by leaving doors open for invaders then when out by snorting too much cocaine