How many games that originated on PS1 have been ported to PC games that are available on GOG? I guess it also counts if the game didn't originate on PS1 but the PC port is clearly based on the PS1 version.

Blood Omen: Legacy of Kain
Deathtrap Dungeon
Disney's Hercules
Gex
Hogs of War
Legacy of Kain: Soul Reaver
Metal Gear Solid
Oddworld: Abe's Exoddus
Oddworld: Abe's Oddysee
O.D.T.: Escape... Or Die Trying
Pandemonium!
Pandemonium 2
Shadow Madness
Street Fighter Alpha 2
Tomb Raider 1+2+3
Tomb Raider: The Last Revelation + Chronicles
Tunnel B1

There was also
Blood Omen: Legacy of Kain
Hogs of War
I can't think of much else that you haven't already mentioned.

Edit: Forgot more Square stuff:
Gex
Deathtrap Dungeon
Legacy of Kain: Soul Reaver
Pandemonium 1 + 2

Legacy of Kain: Soul Reaver was also a PS1 game.
As were Hitman 1, 2 (and 3?) I know 1 and 2 were for sure.

Hitman 1 was pc exclusive. 2, Contracts, and Blood Money were PS2.

I thought the PSX version was a secondary ("enhanced") version - hence why it had the Rik Mayal voice overs.

PlayStation
PAL: 25 August 2000[2]
NA: 29 September 2000[1]
Windows
PAL: 3 November 2000

Interesting and odd at the same time. Must be a tale behind it. Cheers!

Do remakes & remastered ports fit? Then

wikipedia.org/wiki/List_of_video_game_remakes_and_remastered_ports

Please choose those that apply here

Fair enough, I don't know as much as I thought I did.

I don't think they are "port" of PlayStation games.
TR1 was released on Sega Saturn, followed shortly by versions for PC and PS.
PC and PS version of later TR games are almost always released at the same day/week.

No, let's stick with actual ports. Adding in remakes and remasters would open up a quagmire.
The PC games are clearly meant to be working with a PS1 base. There's no way a PC game in 1999 would look like so ugly. Kinda like how iIF both the N64 and PC versions of Star Wars: Shadows of the Empire were released on the same day, it's clearly an N64 game at heart.

Would the Oddworld games count, Abe's Oddysee and Abe's Exodus? They were originally released on PS1 and then on PC shortly afterwards from what I understand.

I can't believe I completely forgot about them.

Wipeout.

As someone who grew up playing PS1 games, this topic is interesting.

Many years ago, I remember seeing a copy of the PC version of Resident Evil at a store. Perfect weapon is another PS1 game that had PS1 release prior to PC. Twisted Metal had PC release for Japanese localization. None of them are legally available digitally, as far as I know.

Mortal Kombat 3 was original an arcade before being ported to consoles, and later PC. I'm not sure what PC version used as a base though.

I believe Rayman was release on PC and consoles (including PS1) around the same time.