Forgot the mention Harry Potter game series, all of them are great, unfortunately, none of them are available for purchase on Steam or Origin or anywhere else. So i'd really like to see them come to GOG.

I would agree with this if GOG and the developer managed to make the game remove its IP blocks. That would be really great!

Pirates of the carribean (2003). (the following of sea dogs 1 - 2000)

Smashing Pumpkins Into Small Piles of Putrid Debris
Pong Kombat series

Off the top of my head:

Magic Candle series
Civilization 1, 2 and Test of Time
SpellJammer
SpellCross (really underrated strategy game in unique setting)
The Legacy - Realm of Terror
Bethesda's Terminator games
Witchaven 1/2
Dark Seed

As I usually say when such threads come up:
Legend Entertainment games (specifically Eric the Unready)
People have already mentioned the Jazz Jackrabbit games
Hercules was a cute little platformer too
Some more platformers: Aladdin, The Lion King, Jungle Book, Pitfall: The Mayan Adventure
Primal Rage in terms of fighting games, I guess?

The Adventures Of Lomax In Lemmingland
American McGee's Alice
Blackthorne
Blade Runner
Blood Omen: Legacy Of Kain
Callahan's Crosstime Saloon
Command & Conquer (a.k.a. Tiberian Dawn) + The Covert Operations + Sole Survivor
Command & Conquer 2: Tiberian Sun + Firestorm
Command & Conquer 3: Tiberium Wars + Kane's Wrath
Command & Conquer 4: Tiberian Twilight
Command & Conquer: Red Alert + + [url=https://www.gog.com/wishlist/games/command_conquer_red_alert_the_aftermath]The Aftermath
Command & Conquer: Red Alert 2 + Yuri's Revenge
Command & Conquer: Red Alert 3 + Uprising
Command & Conquer: Generals + Zero Hour
+ [url=https://www.gog.com/wishlist/games/diablo_unearthed_arsenal]Unearthed Arsenal + Hellfire
Diablo II + Lord Of Destruction
Discworld
Discworld II: Mortality Bytes!
Discworld Noir
Dungeon Master + Chaos Strikes Back
Dungeon Master II: The Legend Of Skullkeep
Fade To Black
Flashback: The Quest For Identity
Freddy Pharkas: Frontier Pharmacist
Freelancer
Grand Theft Auto + London 1961 + London 1969
Grand Theft Auto 2
Grand Theft Auto III
Grand Theft Auto: San Andreas
Grand Theft Auto: Vice City
Heart Of Darkness
Homeworld: Cataclysm
Indiana Jones And The Infernal Machine
Indiana Jones And The Last Crusade: The Graphic Adventure
It Came From The Desert + Antheads
Jazz Jackrabbit
Jazz Jackrabbit 2
+ [url=https://www.gog.com/wishlist/games/holiday_lemmings]Holiday Lemmings + Oh No! More Lemmings
Lemmings 2: The Tribes
Lemmings 3D
The Lemmings Chronicles (a.k.a. All New World Of Lemmings)
Lemmings Paintball
Lemmings Revolution
The Lost Vikings
The Lost Vikings 2: Norse By Norsewest
Marathon
Marathon 2: Durandal
Marathon Infinity
Max Payne
Max Payne 2: The Fall Of Max Payne
Myst III: Exile
Myst IV: Revelation
Myth: The Fallen Lords
Myth II: Soulblighter
Myth III: The Wolf Age
The Neverhood
No One Lives Forever
No One Lives Forever 2: A Spy In H.A.R.M.'s Way
Oddworld: Munch's Oddysee
Oni
Powermonger
Prince Of Persia
Prince Of Persia 2: The Shadow & The Flame
Prince Of Persia 3D
Resident Evil
Resident Evil 2
Resident Evil 3: Nemesis
+ [url=https://www.gog.com/wishlist/games/starcraft_stellar_forces_expansion_pack]Stellar Forces + + [url=https://www.gog.com/wishlist/games/starcraft_retribution]Retribution + Brood War
Starlancer
The Thing
Tomb Raider: Anniversary
Tomb Raider: Legend
Tomb Raider: Underworld
Warcraft: Orcs & Humans
Warcraft II: Tides Of Darkness + Beyond The Dark Portal
Warcraft III: Reign Of Chaos + The Frozen Throne

Top priority:
MechWarrior 2 + exp
MechWarrior 3 + exp
MechWarrior 4 + exp
Turok 2
Call of Cthulhu: Dark Corners of the Earth

Medium priority:
MechWarrior
SWAT 4
Alien vs Predator 2
Future Cop: LAPD
Space Hulk

Low priority:
Prey
Pariah
Take no Prisoners
Space Hulk: Vengeance of the Blood Angels (Space Hulk 2)
Ignition

Damn son I hope that was a copypasta

Lemmings (the lot)

And from the PlayStation: Tenchu and the original three Spyro the Dragon games.

Not going to post a list but would like to see more and better chess games here.

XCOM - Enemy Unknown/Enemy Within
Fallout 3/New Vegas/Oblivion/Skyrim
Bioshock series
Civ series
Paradox - Crusader Kings 2/Victoria 2/Cities Skylines/EU IV
Batman Arkham series
The Movies
Jurassic Park Trespasser (for shits and giggles)
Older Total War games (Shogun 1+2, Medieval 1+2, Rome)
KOEI strategy games (historical series, Nobunaga, Liberty or Death, Romance of the Three Kingdoms, etc)
Silent Hunter sub series

Get all of those here and I'll be happily occupied for the next 200 years.

Kohan 1+exp
Kohan 2

Sudden strike, the whole lot

Imperium Galactica 2

Space Empires 5

Rise of legends, Rise of Nations

Supreme Commander (although it is slightly less ancient)

edit: and Harpoon or Jane's Fleet command

My list is simple.
No One Lives Forever
No One Lives Forever 2
Current Bethseda RPGs

Bring back Duke Nukem - I understand GOG used to have it - that would be an instant purchase for me. Also Heretic and Hexen - I missed out on that PC game era and would so love to get them.