The original System Shock 1 and System Shock 2
I'm really looking forward to see System Shock Remastered finally, after so many years, released this summer. Both SS & SS2 were just so immersive all those years ago (1994 for SS, 1999 for SS2), and from the game play video, it looks like Nightdive Studios really kept the feel of the original. I give them credit for stopping their first attempt before it was done, and completely restarted production, so that they could remain true to the original. That costs money, and not many studios would do it. I haven't yet had time to play the free demo available on Steam, but I hope to get to it soon.
The original SS, from Origin back in 1994 was still an MS-Dos game that you had to make a boot disc to be able to run it. Anyone remember boot discs? But back then, it really wasn't a big deal, as many games required a boot disc to run. SS2, from Looking Glass in 1999, ran on Windows 95 or 98, and required a 4 MB (4 MB!) video card, like the 3DFX Voodoo card. Both games had a sense of discovery, exploration, and tension as you slowly made your way through the environment; with Shodan mocking you. The closest any game has come to that feeling was the first Bio Shock game, at least for me. I never played Alien Isolation, but it seems like that might have a similar mood going for it.
Boot Disc Instructions