Myth The Fallen Lords and Myth II: Soulblighter. These games really, really should be here

Oldies

Dungeon Master (+ CSB + DM2)
Heretic/Hexen series
The rest of the emulated Cinemaware games, especially It Came from the Desert
TimeQuest
NOLF series
The Settlers (the first one)
Just Cause
Wizardry 1-5
PS - seeing the current release: Terminator Future Shock and Skynet!

Not-So-Oldies

The newer Deus Ex games
Everything DOOM

... come to mind first.

Generally it would be cool to have more emulated classics, esp. from Amiga, but there the license situation (Kickstart ROMs) is a mess.

OK here's my updated list:

Top priority:
Mechwarrior 2, 3, and 4 with all expansions (possibly #1 as well)

High priority:
Project IGI: I'm Going In
Tom Clancy's Splinter Cell: Pandora Tomorrow
Heavy Gear 2
Space Hulk 1 & 2

Medium priority:
Prey (2006)
Oni
Alien vs Predator 2
Laser Squad

Low priority:
Future Cop: L.A.P.D.
Take no Prisoners

On a side note, I would also very much like GOG to offer games that are, or will be, available on other platforms: Command & Conquer collection, HALO collection, Heretic and Hexen series, Max Payne series, WH40K: Space Marine, Rise of Nations, maybe newer Deus Ex games like Human Revolution and Mankind Divided (I don't know if they are good or would appeal to a fan of the original game).

Also: I have not included No One Lives Forever 1 & 2 in my list, because I have played them in the past and I have no particular urge to revisit them now, so technically speaking they are not among the games that I wish most that GOG would bring to their store. If the title of this thread was "What games you think most should be on GOG", they'll go straight at the top of the list.


*** EDIT ***
I am a bit undecided on this issue, and even more about console or even arcade games on GOG (if it's feasible at all, that is), given the site's strong focus on PC gaming, but as a past Commodore user, I think I would be happy if GOG gave me the possibilty to revisit at least some oldies (for example, for Space Hulk and Laser Squad I would actually prefer the Amiga versions, for nostalgic reasons of course), maybe even some C64 games.
And obviously I am talking about making things legally; if you don't care about such technicalities, then finding what you need on the Internet is super-easy.

Assassin's Creed serie
Borderlands serie
Dead Island
Batman
Far Cry 3 and mores
Dark Souls
Monster hunter world
Dungeon siege
Hellgate London
Alpha Protocol
Dawn of War
Tomb raider reboot

I'll third Wizardry 1-5, mainly because it would give me a reasonable way to legally own Wizardry 4.

(Only problem is that the DOS versions of 1-3 have a bug that makes stats much more likely to decrease at level up, resulting in a lot of young elves dying of old age.)

Fade to Black (1995).

I'd love to see the following here and all would be an instabuy;

Skyrim
Dragon Age 2
Dragon Age: Inquisition
Northmark: Hour of the Wolf

Comic Book Games: Batman, Spawn, DC, Marvel, Dark Horse, Vertigo, etc.

Dragon Warrior/Quest Games (bundle old port/with mobile releases)

Ninja Gaiden/Shinobi games (and like games)

Racing Games (Cars, MX, ATV, etc.)

Star War Games

Flying/Tank Simulations

Fishing and Hunting Games

1. Ragnarok Battle Offline. Some random gameplay on yt: https://www.youtube.com/watch?v=eiKE5grgrWU
Its one of my favorite beat'em up / rpg mixtures, yet there is no way to get it legally nowadays - its fan-made japanese game, based on ragnarok online universe that belong to other company. When it was in development, they had permission to use it commercially (they even made few paid expansion packs after game's release), but then something has gone wrong and game disappeared from japanese digital stores (and it was never sold in english, if Im not mistaken - all translations were fan-made).
2. Gotcha! Extreme Paintball. Random yt footage: https://www.youtube.com/watch?v=i0fEn3CWfTU
I have warm memories regarding this one, coz it was the only shooter I could play without losing to everybody (lol). Feature multiple game modes (team based such as tdm/ctf, captain and solo like king of the hill) and decent AI (not great, not terrible). Sadly, I've lost my CD with it (but even if I didnt, Im unsure if I could play it nowadays - it had some drm that required disk to present in cd-rom to play).
Both of these present in community wishlist, but... well... they are *kinda* niche, so very few people has voted for these.
https://www.gog.com/wishlist/games/ragnarok_battle_offline
https://www.gog.com/wishlist/games/gotcha_extreme_paintball

A few games that I'd like to see on GOG:

Call of Duty World at War

Medal of Honor Airborne

Battlestations Pacific

Battlestations Midway

Prisoner of War

The Great Escape

Godfather

Godfather 2

Scarface: The World is Yours

Severance

Chicago 1930

This Land is My Land

Lord of the Rings Conquest

Lord of the Rings Return of the King

NOLF

I can't believe someone else remembers this! :D
One of my favourites of all time, too. The mechanics are unlike anything I've ever seen in a beat-'em-up before (though I suppose the Kunio-kun games are vaguely similar)

Didn't know it's unavailable nowadays. I hope it doesn't fade into obscurity... Please GOG, adopt this gem of a game. :c

GOG, please get Heretic and Hexen.

Why on earth is this still not here yet?

Same goes for Commander Keen. These are no-brainers!

Alien Trilogy
CLAW
Cold Fear
Colin McRae Rally 2.0
Crazy Taxi
Diablo II
Die Hard Trilogy
Drakan
Duke Nukem 3D
Exhumed / Powerslave
Grand Theft Auto
House Of The Dead
James Bond 007: Nightfire
Max Payne
Metal Gear Solid
Midnight Club II
Need For Speed
Nightmare Creatures
No One Lives Forever
Resident Evil
Test Drive Unlimited
The Sims
Warcraft III

A few more games as they've come to mind...

Enemy Front

Deadly Dozen 1 & 2

Company of Heroes 1 & 2