1994's FPS-RPG, System Shock, is an important game. It was an influence on not just BioShock and its sequels, but also a variety of game series in between, like Half-Life and Deus Ex. It was also a bitch to play on modern PCs, which is fortunately something this re-release should help with.
The announcement from GOG talks about what's new in this version:
System Shock: Enhanced Edition now comes with official support for resolutions up to 1024x768 (compared to the original 640x480), and a native 854x480 widescreen mode. Gameplay is streamlined with a toggleable mouselook mode, including more intuitive inventory and item management. Combined with assorted bug-fixes and remappable controls, System Shockis now truly enhanced. Still, some gaming experiences are truly worth preserving, so you can also return to the authentic 90's gameplay with System Shock: Classic - ready for modern systems, completely unaltered in all other aspects.
There's also a trailer:
And a couple of comparison shots:
You can grab the game here. Also, fun fact: today's actually the game's twenty-first birthday. Might as well get out there for a drink, System Shock, you deserve it.