I've been recently been thinking about Arkane Studio's Prey which is a immersive sim, with a pretty good rogue like dlc, that probably has one of the strongest hooks of any game I've played. If you liked Halflife, System Shock, or Deus Ex it's definitely worth a play.
Are there any titles that might not have been commercially successful that you feel everyone should give a shot?
Eternal Darkness is one of my favourite GameCube games. I feel like it might be long enough ago that they could do a remake with modern sanity effects.
And Halo Reach is my favourite Halo game, loved it.
Nightdive Studios (they, among other titles, remastered System Shock, which has received pretty good reviews) wanted to remaster Eternal Darkness, but Nintendo - who owns Eternal Darkness - doesn't want that to happen.
Also, the original developers of Eternal Darkness want to create a spiritual sequel, but that seems to be… an eternal project. Check out Shadow of the Eternals, if you want to follow that project. There's a gameplay video from like 2013 or 2014.
Haven't they tried to get the spiritual successor off the ground on a bunch of different occasions? Are they still trying?
They have tried twice. And yes, they still want to make it happen. But last time I heard the team made a game they need to support for few years (some kind of online game), so it's going to take some time before they can try again.