Considering all the versions of System Shock:
- The original DOS version of System Shock, which came on floppy disc,
- The extended DOS version that came on CD-ROM,
- The Apple Macintosh version of the game,
- The unofficial (and not very legal) Windows package of the game plus various mods and DOSBOx that used to be available,
- The official (and totally legal) Windows package of the game plus various mods and DOSBOx that used to be available,
- The official port of the Apple Macintosh source code to Windows,
- The unofficial fan-made port of the Apple Macintosh version to Windows,
- The upcoming official remake of the game for Windows,
- The upcoming unofficial remake of the game for Windows (which is due soon),
we probably only need a virtual reality version, a Linux version, and a version of the game that comes with pre-order bonuses, and System Shock will have done it all!
It's like Blood, sort of. That (great) game came out first for DOS, then when Windows XP came along it was very difficult to get it working on modern systems, even if your PC was fast enough then to play the game at full speed in DOSBox, so several ports of the game (not source ports though, as Blood's source code was never released) were began, including at least two in the Doom engine. I think the only one that was worth bothering with was ZBlood, but I might be mis-remembering it. And now we have three ports to look forwarded to; the very good BloodGDX*, which is almost perfect on the single player side (I've not tried the multiplayer), the also very good NBlood (https://forums.duke4.net/topic/10456-release- … ased-on-eduke32), and the upcoming official port of Blood, from Night Dive Software (http://www.nightdivestudios.com/)
* BloodGDX is no longer available as a download itself, it's now part of the really good BuildGDX, that plays Blood, TechWar and Witchaven:
https://m210.duke4.net/