Another timeless classic. And this one is probably the best title in the entire franchise. Anything from the settings, atmosphere, and gameplay is just top-notch, with some relatively minor exceptions. Even better, the player is very much a "mere mortal" in this game, with no skills to learn. The story is also much better and more grounded compared to later titles, and the finale is also much more fitting and satisfying too. Most of the game's somewhat-minor drawbacks and quirks can be dealt with by mods, while still maintaining the overall experience of the game.
Considering the developer/publisher of the series and their attitude to game preservation, yeah, the chances of this one making its way to GOG is what I'd call "pretty slim". One can only hope for the best outcome.