Das Geisterschiff
https://www.gog.com/wishlist/games/das_geisterschiff

Not exactly "turned down", but NISA has de-confirmed a gog release for killer7.

https://steamcommunity.com/app/868520/discussions/0/3374780959382027688/#c3374780959382119922

Somehow I can't see devs and publishers lining up in front of gog HQ going "Please, please, PLEEEEASE take our money, Mr Iwinski! If we're lucky we can sell one tenth of what we made on Steam if you accept us on gog!"

Somehow you shall not see them, believe me, as no one shan't. And I have great doubts that 'pan Iwinski' still has full control over 'his' company ;)

Here's the list so far. Please vote!

40 Winks
7 Mages
8BitBoy
ADventure Lib
The Adventures Of Bertram Fiddle
Aeternum
Aground
ALLTYNEX Second
Alpha Polaris
Always Remember Me
Amber's Magic Shop
Another Star
AR-K
AR-K: The Great Escape
ARMED SEVEN
Ashworld
Aurion: Legacy Of The Kori-Odan
Aztez
Betrayer
Bible Adventures
Binaries
Bionic Heart
Bionic Heart 2
Black Ice
Blossom Tales: The Sleeping King
Bolt Riley: A Reggae Adventure
Breath Of Death VII: The Beginning
Bubble Ghost
Bullet Heaven
Bullet Heaven 2
C14 Dating
Call Of Cthulhu: The Wasted Land
Castle Of Shikigami
Central Intelligence
Chamber Of The Sci-Mutant Priestess
Chaos Control
The Charnel House Trilogy
Cherry Tree High Comedy Club!
Cherry Tree High I! My! Girls!
City Of Brass
The Consuming Shadow
Cranks And Goggles
Croixleur Sigma
Crystal Story II
Cthulhu Saves The World
Cursed Lands
Curses 'N Chaos
Cute Things Dying Violently
Daemonsgate
Darius Burst: Chronicle Saviours
Dead End Job
Dead Pixels
Dead Pixels II: Straight To Video
Deathsmiles
Deep Ones
Deity Quest
Deja Vu: A Nightmare Comes True (MacVenture Series)
Deja Vu II: Lost In Las Vegas (MacVenture Series)
DELTAZEAL
Demetrios: The Big Cynical Adventure
Detective Grimoire
DoDonPachi Resurrection
Dominique Pamplemousse: It's All Over Once The Fat Lady Sings!
Dominique Pamplemousse 2: Combinatorial Explosion!
Dorke And Ymp
Dr. Dungeon's MADMAN!
Drifting Lands
Duke Grabowski, Mighty Swashbuckler!
ELF
Empire Architect
Epic Battle Fantasy
Epic Battle Fantasy 2
Epic Battle Fantasy 3
Epic Battle Fantasy 4
Epic Battle Fantasy 5
Eryi's Action
ESCHATOS
Eternam
ETHER VAPOR Remaster
eXceed: Gun Bullet Children
eXceed 2nd: Vampire REX
eXceed 3rd: Jade Penetrate Black Package
Excelsior: Phase One - Lysandia
Excelsior: Phase Two - Errondor
Exodus
EXZEAL
Fairy Bloom Freesia
The Fall Of The Dungeon Guardians
Flatspace
Flatspace II: The Rise Of The Scarrid
Flinthook
The Flower Shop: Summer In Fairbrook
The Flower Shop: Winter In Fairbrook
Game Tengoku CruisinMix
Das Geisterschiff
GemCraft: Chasing Shadows
GIGANTIC ARMY
Gladiabots
The Goalkeeper
The Great Escape
Groundskeeper 2
Gunslugs
Gunslugs 2
Gunslugs 3

Hatred
Haunt The House: Terrortown
Heileen: Sail Away
Heileen 2: The Hands Of Fate
Heileen 3: New Horizons
Heileen 3: Sea Maidens
Heirs And Graces
Her Majesty's SPIFFING
Hero Siege
Heroes Of Loot
Heroes Of Loot 2
Heroine's Quest: The Herald Of Ragnarok
Homesick
Hostage: Rescue Mission
A House Of Many Doors
Hydraulic Empire
I Can't Escape: Darkness
Immortal Defense
INC: The Beginning
The Infectious Madness Of Doctor Dekker
Iron Commando: Koutetsu No Senshi
Ittle Dew 2
Jim Power: The Lost Dimension
Joshua And The Battle Of Jericho
JUDGEMENT SILVERSWORD: Resurrection
KAMUI
Kelvin And The Infamous Machine
King's Table: The Legend Of Ragnarok
KUSO
Larry Elmore: SnarfQuest Tales
Last Rites
The Last Time
Legend (1994)
Loren The Amazon Princess
LOVE
Love Bites
Lucius 2: The Prophecy
MagNets
Marco Polo
Meganoid
Meganoid: Grandpa's Chronicles
Mercenary Kings
MINUS ZERO
Missile Cards
Mushihimesama
Mystical
Nelly Cootalot: Spoonbeaks Ahoy!
Nelly Cootalot: The Fowl Fleet!
NeonXSZ
Neoteria
Never Forget Me
Nicole
Nimbus
Ninja Senki DX
One Finger Death Punch
Penny Arcade's On The Rain-Slick Precipice Of Darkness 3
Penny Arcade's On The Rain-Slick Precipice Of Darkness 4
Planet Stronghold
Planet Stronghold: Colonial Defense
Pocket Kingdom
PONCHO
Prophecy: The Viking Child
Pushover
QUALIA 3: Multi Agent
Quarantine Circular
Queen Of Thieves
The Quest
＜/reality＞
RefleX
RefRain: Prism Memories
Regions Of Ruin
Rex Rocket
A Rite From The Stars
Roommates

Seasons Of The Wolf: Bad Blood
Secret Little Haven
Shadowgate (MacVenture Series)
Shmups Skill Test
SiC
Sir Questionnaire
Siralim
Siralim 2
Siralim 3
The Slaughter
Sleepwalker
Snakebird
Space Grunts
Space Invaders Extreme
Speedy Eggbert (a.k.a. Speedy Blupi)
Speedy Eggbert 2 (a.k.a. Speedy Blupi 2)
Spirited Heart
Spirited Heart Girl's Love
Spiritual Warfare
The St. Christopher's School Lockdown
Stardash
STARDROP
Starward Rogue
Steam Marines
Steam Marines 2
Steam Marines 3
STEEL STRIDER
Subsurface Circular
SunAge: Battle For Elysium
Super 3-D Noah's Ark
Super Rad Raygun
Superbrothers: Sword And Sworcery EP
Supercharged Robot VULKAISER
Sword Of Asumi
They Bleed Pixels
Thomas Was Alone
Time Gate: Knight's Chase
Tokyo Dark
Traum
TRIZEAL Remix
Tunnel B1
TV Station Manager
The Uncertain: Episode 1 - The Last Quiet Day
The Uncertain: Episode 2 - Light At The End
Underworld Ascendant
The Uninvited (MacVenture Series)
Universal Boxing Manager
Vera Blanc
Vidar
Vigilantes
Void And Meddler
Volume
Warbanners
The Warlock Of Firetop Mountain
Where Time Stood Still
Willy-Nilly Knight
Wings Of Vi
Wizorb
WOLFLAME
XIIZEAL
Yatagarasu: Attack On Cataclysm
ZANGEKI WARP
Zavix Tower
Zigfrak

Games whose developers/publishers aren't interested in releasing on GOG:

The Binding Of Isaac
The Binding Of Isaac: Rebirth
Hidden Folks
killer7

Thanks. I was so clamoring for this, but eventually never played it.

Wait a god-damn-second!
GOG turned down the opportunity to release The Binding Of Isaac and The Binding Of Isaac: Rebirth?!?!?!?!?!?!? O.o
There is an invasion of tasteless anti-games hentai shit and these awesome GAMES are turned down!?!?!?!?!?! O.o
Who the fuck is crazy here?!?!?!??! O.o

As far as I know it wasn't turned down, but the developer wasn't interested in releasing it here. Can't find the quote at the moment though.

Ed is a [Negative Creative Epithet] to begin with, while the publisher Niclas has never been interested in GOG, as otherwise I feel we'd have seen plenty of Nifflas games and perhaps Cave Story by now.

It isn't a GOG problem.

That's what I thought so far. It's makes a HUGE difference if something is turned down by GOG and if the developer doesn't want to release on GOG.

So, please, people posting lists let's call the things what they are.
If I enter a thread called "Games GOG Turned Down" and see a list of games, those that are on the list are "marked" as something that GOG doesn't want in their catalog.

Holy shit, didn't know they rejected X-com-em-up Vigilantes.

Here's a possible update on AI War 2 making its way to GOG after all:
Q: Obviously Steam is the biggest PC games platform, but what’s your experience like on other digital storefronts like GOG?
A: It’s been extremely positive. I hope to be working with GOG soon with AI War 2. They carry the original, as well as some of our other titles, and they’ve been by far our #2 platform.
https://nichegamer.com/2018/12/07/chris-park-interview-arcen-games-ai-war-2-and-visibility-on-steam/

And regarding Edmund McMillen's titles on GOG:
Q: I have an awkward question, why do not you publish your games on gog?
A: im lazy.. :|
https://twitter.com/edmundmcmillen/status/1070457360781463552