Atomic Heart
>>Trailer

I have no words for this game, it has huge potential.

I think GOG needs more First Person Puzzler games. We have QUBE & Magrunner: Dark Pulse, but little else whose gameplay "is more Portal than Myst". All three suggestions below are "Very / Overwhelmingly Positive" and I'd insta-buy all three on GOG.

Quantum Conundrum - It was actually directed by Kim Swift (lead designer of Portal). Instead of portals, you control time & gravity with "heavy, fluffy, reverse and slo-mo" dimension shifting. Puzzles are good, music & voice acting is great (John de Lancie aka "Q" from Star Trek). General humor and tone is good.
https://store.steampowered.com/app/200010/Quantum_Conundrum/
https://www.gog.com/wishlist/games/quantum_conundrum

The Talos Principle - Over 1,000 wishlisted already, needs (and deserves) way more. Phenomenal game where pretty much everything is just about perfect (puzzle difficulty & ramp-up, visuals, soundtrack, optimisation, philosophy, etc). It's by Croteam (who made Serious Sam so they're not totally opposed to selling their games here).
https://store.steampowered.com/app/257510/The_Talos_Principle/
https://www.gog.com/wishlist/games/the_talos_principle

The Turing Test - I describe it as "a cross between Portal, The Talos Principle, Julia Among The Stars and "2001: A Space Odyssey". Definitely one of the better Portal style games that's pretty relaxing to play.
https://store.steampowered.com/app/499520/The_Turing_Test/
https://www.gog.com/wishlist/games/the_turing_test

Castle Crashers
>>Trailer
>>Review

Dandara: https://www.gog.com/wishlist/games/dandara

Wings Of Vi
>>Demo
>>Trailer
>>Review
>>Soundtrack
>>Official Site

The list so far:

1001 Spikes
Agony
Anarcute
Armored Brigade
Atomic Heart
Axiom Verge
The Binding Of Isaac
The Binding Of Isaac: Rebirth
Bleed
Bleed 2
Castle Crashers
Cat Quest
Cave Story+
Celeste
City Of Brass
Creeper World
Creeper World 2: Redemption
Creeper World 3: Arc Eternal
Dandara
Delver
Detention
Disco Elysium
Dominions: Priests, Prophets And Pretenders
Dominions 2: The Ascension Wars
Dominions 3: The Awakening
Dominions 4: Thrones Of Ascension
Dominions 5: Warriors Of The Faith
Drums Of War
Dungeons Of Dredmor
Escape Velocity: Nova
Euro Truck Simulator
Euro Truck Simulator 2
Far From Noise
Flinthook
Fortune Summoners
Gunpoint
Hidden Folks
ICEY
Kero Blaster
The Last Night
LISA
Lost Ember
Monster Prom
N++
Nidhogg
Nidhogg 2
Northgard
Old Man's Journey
One Finger Death Punch
Ori And The Will Of The Wisps
Overcooked
Pharaoh Rebirth+
Qbeh-1: The Atlas Cube
Quantum Conundrum
Rabi-Ribi
Rakuen
Rex Rocket
Salt And Sanctuary
Scorn
The Seven Years War
Skullgirls
Spelunky 2
Starscape
Subnautica
Super Meat Boy
Super Meat Boy Forever
Superflight
SYNTHETIK
The Talos Principle
They Are Billions
Traum
The Turing Test
Unexplored
Warbanners
Way To The Woods
Wings Of Vi

Personally I wanna see indies show up that have like 300+ votes, of course.

Cthulhu Saves the World

https://www.youtube.com/results?search_query=cthulhu+saves+the+world
https://www.gog.com/wishlist/games/cthulhu_saves_the_world

this and Breath of Death VII are a pack on Steam.

They Bleed Pixels: https://www.gog.com/wishlist/games/they_bleed_pixels

Antichamber
>>Trailer
>>Review
>>Soundtrack
>>Official Site

Insanely Twisted Shadow Planet: https://www.gog.com/wishlist/games/insanely_twisted_shadow_planet

Shrug Island - Wishlist GOG.com

Shrug Island

The Dream Machine: https://www.gog.com/wishlist/games/the_dream_machine