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?
Underappreciated for sure, but to be fair, it's super repetitive. If they'd added a secondary component or loop where you could black market trade or participate in the economy of the game some how to drown out the monotony of breaking the same ships over and over, I'd have played it more.