being serious, do not try dark souls, demon souls, or any other game that has a reputation for being too hard or needing an easy mode. red dead redemption 2 is a pretty engaging game and is fairly easy, but it can be pretty bloody and language so best to not play with kids. i would also say the witcher series (very engaging), but has some violence and that sexy sexy time with women. mafia definitive edition is a great game with a great story. mature, but it is fairly easy, there are difficulty options. it is very driving focused, and the hardest mission, i would say, would be the race mission.
among us is a nice game. not that "serious" but can be, with like top tier liars and detectives.