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?
I haven't played Stalker but I did finish Into the Radius which is heavily inspired by it.
Oh Into The Radius made me shit myself in fear more times than I'd like to admit
Probably one of the best vr titles I've played. You really feel the isolation.