What I own on GOG that I haven't touched
Ultimate 4: Quest of the Avatar
-I've not played it, no opinion. I think there's a Master System version of this I might try someday. I'm not keen on
Ultima because of its weird isometric view, and also the whole "you have to be the goodest good guy ever to win".
Syndicate Plus (not sure if this counts)
-Eh I'd play the PS1 version actually, not a huge fan. I put a little time into this back in 1997. I also put time into the original
Syndicate. I like the concept of these games, but they don't stick for me.
Realms of Arkania 3
-Never played. I think I own it on GOG though.
Gorky 17 (AKA
Odium)
-I played this circa 2000. I own a physical copy and a GOG copy. I didn't beat it. I remember it was hard as balls. Or maybe I was just weak as balls. You'd probably like it.
Septerra Core: Legacy of the Creator
-I've never played this. I have a distaste for wannabe western-developed "JRPGs". Just like when westerners try to drawn anime it never looks right.
Nox
-Not played, but always looked good. I own it physically and on GOG.
Icewind Dale Complete
-Back in 2003 I put about 20 hours into this game. It was good. Unfortunately I spent a week away from the game due to life shit and couldn't get any traction to pick it back up. I'd like to go back and beat it someday. I've got the physical and GOG version.
Icewind Dale 2 Complete
-I've never played, but I own it physical and on GOG.
Enclave
-I've got this on original Xbox. It's a hack 'n slash action game. I've not beaten it.
Temple of Elemental Evil, The
-Very high pedigree! I've not played the PC variant. I used to run the original D&D campaign long long ago. I not only own a physical version of this on PC, but also the digital GOG version, and I even own the boardgame version:
I would only recommend TotEE if you are hardcore into D&D though. It's made for D&D nerds.
Forgotten Realms: Demon Stone
-I beat this earlier this year. It's not an RPG at all. It's a beat 'em up. I own the PS2 version.
Neverwinter Nights: Enhanced Edition
-I own this on physical and on GOG. Never played it.
Dungeons & Dragons: Dragonshard
-Own this on GOG. Never played it.
Two Worlds Epic Edition
-Own this (and its sequel) on 360. Never played it.
Arcanum: Of Steamworks and Magick Obscura
-I own the physical and GOG version of this. I put about 15 hours into it back in 2004. It's decent. I didn't beat it.
So yeah I own a lot of PC games I've hardly played. As to your question - out of that bunch Gorky 17 might be the best choice for your tastes.