Cities: Skylines 2 and osu! seem like the easy picks for me, because there's probably an endless amount of fun to be had in both. Minecraft is also a likely pick, precisely for the same reason. Grim Dawn is probably my fourth pick, because it seems if you want to try out everything interesting in the game, it'll take thousands of hours. For my last pick, I'm not entirely sure. It's possibly between Crusader Kings III, Left 4 Dead 2 (if good company is assured), and some Total War game (probably Three Kingdoms based on those I've played), but Left 4 Dead 2 is the only one I've played enough to know well enough what I'd be getting into in the long term. I suspect Crusader Kings III would be the least risky pick, so I'll go for that.
As always, I'm sure I've missed some great picks, so my list will probably look a bit different in some years, even if restricted only to games released by the time I'm posting this.
