What games can you recommend that didn't get the appreciation that they deserved?
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?
Nice, that's one I have in my library not yet installed. Bought it when there was a cheap bundle with others by that company, but was mainly looking at The Place which kinda turned me off of those style games. I'll have to be sure to give it a shot now.