Nier Automata ALL the way!!!! Such a fantastic and mouth opening game, with smooth and fun combat I mean, depends again... "why" The decision? Going to stream it ? Chill it ? Or just need something to engross yourself with ?
I strongly suggest either Dark Souls 3 or Nier Automata. While Dark Souls isn't too heavy on a story... it does have plenty of lore and quite a large area to explore. It is quite difficult though so beware when facing anything new in there as it will most likely kill you fast.
Nier is one I'm currently playing and it's quite good so far. While it don't directly tie in with the original Nier (yet, as I don't believe I'm too far into it) it does have quite an interesting story. Fights can be difficult early on but become a bit easier when you learn the mechanics. Although some bigger enemies can still tank you pretty good and bosses are quite a thing as well. It also has a pretty in depth story with numerous endings as well. Some endings are just stupid though (damn mackrel) while others are more like the main endings. I haven't reached any main ones yet, but I have heard some interesting things about them and how there's a lot of thinking and feels involved.