I'll second RoboPond about Mass Effect coming here. As I've said in the past, Mass Effect 1 and 2: Deluxe Ed are both on Steam anyway, not Origin exclusive. And are highly desired by the community. Of course I'm sure GOG would love to have them, and EA is the hold-up. Same with Dead Space 2 - on Steam.

Axiom Verge; Doom 3 + RoE originals; Doom 2016/Doom 4; Astroneer; Commander Keen series (space-y or no?); XCOM 2 (may not be space-y enough but has that association)

Prey 2006
Halo PC titles

if legal issues could be worked out, Star Trek games; Dune games; AvP2 and 2010; Ascendancy; Alien Trilogy; Starship Troopers games; Elite games like AB2012 mentioned

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as for space games already on GOG (some of this list fit better than others, space-wise): you could put Unreal Gold and 2 on sale, maybe Beyond Good and Evil, the Red Faction series, Alien Shooter series, Shogo, Quake series, Star Wars titles (if they weren't already on sale last week ;), Giants Citzen Kabuto maybe, Outcast series, FTL of course

(of course I know you can't usually put games on sale very quickly, it all has to be approved by the publishers)

- Elite Plus
- Freelancer
- Frontier: Elite 2

Just recently got around to playing Dead Space. It's an innovative collision of Event Horizon and Resident Evil, total recommendation if you've never spent some quality time on the USG Ishimura.

At one point in the 90s, I tried one of the Wing Commander games. I had played X-Wing and TIE Fighter before, and compared to those, Wing Commander felt like I was rotating in place (no feeling of speed or velocity).

I'm missing Elite: Dangerous. And FTL, Halcyon 6, Utopia, Starbound and so many more here...

Maybe a little bit controversial: (Privateer 2) The Darkening.
Even more than Wing Commander 3 & 4 (sorry WC fans), especially because of its freedom and its weirdness.
When Star Citizen was announced, I would have been more intrigued if it was in the vein of The Darkening instead of Squadron 42.

I wonder why dead space is so expensive in GOG

I'm going to be that guy and point out that Stellaris is real-time, not turn-based. I wish it were, I tend to prefer turn-based when I can find it.

There's always the Master of Orion series if you don't want real-time!

Here is my summery of these games, as someone who has touched all of them at some point (and either bought on here, Steam, or physical copy). Just writing this because I love Space games :).

No Mans Sky: Personally I've found it an excellent experience even prior to patches in a same way going outside for a walk feeling a fresh breeze is excellent. Even with all those added gameplay elements due to constant patching it certainly is not a game for everyone. If you like walking a lot or going to different places and games that are slower paced than Minecraft you will love this game. If you like action/story based games or fast paced games that require quick reflexes like Terraria then stay away. No Man Sky is the perfect game to play on a rainy day, in my opinion.

Stellaris: Having played around 80 hours, I think that Stellaris is probably the greatest 4X game of all time (above and beyond MOO2 IMHO). But like most great games, its the mods that elevate it. Even if you just like RTS games but don't like 4X games I think its worth a try on a discount.

Freespace 2: Greatest space game of all time with some of the greatest (record beating) mods of all time. Probably worth several GOG blogposts IMHO. As the game engine got open sourced decades ago, there are many great things added to the game, that should appeal to gamers both old and new. For starters, buy (or get gifted) the game, install it inside your directory of choice and then get Knossos and just follow the instructions for the potentially best experience that you can have with the game. Have fun! (I wrote this last year but I still intend to make a huge FS2 giveaway happen at some point regardless of the free GOG-goodness they're doing right now :)!)

Wing Commander series: Freespace 2 might be one of those flawless games, but it probably wouldn't exists without the Wing Commander series, which paved the way for many of the other space games to come and certainly made the whole subgenre atmospheric games more mainstream friendly, especially with the use of Full Motion Video later.

Dead Space: The first Dead Space was so scary for me that I couldn't finish it and thats a hell of a accomplishment and I am not usually scared easily by a game. The other Dead Space games aren't really scary in my opinion.

X-Series: Comparing the X Series with Bucket Wheel Excavators seems apt. They're both huge, very bulky with lots of things that makes them function, are very slow but extremly highly sophisticated and respected by everyone who had experience with them.

My personal X ranking, top is highest ranking:

X3: Albion
X4 - Foundations 2.0 (I wait until DLC release and the next large patch)
X3: Terran Conflict
X2
X-Tension
X1
X3: Reunion
(I forgot about X-Rebirth, but I haven't played as much of it to place it anywhere, after years of updates it certainly ain't terrible anymore. You can think of it as a more Sophisticated X1 now.)

Homeworld series: Last but not least, its good old HW. I love those games and I own all the games on physical copies. I still play some of the mods every once in a while and they're still an excellent time. What not many people know, it also has a lively chinese community that I do enjoy reading up on, so with that in mind it has for sure a very diverse community. I can conclude that even just HW2 can universally captivate the minds of many people and that is probably the biggest praise for any game and the devs that I can voice and a hell of a huge achievement. The Remastered version for both the HW games and Cataclysm (called HW: Emergence now) are a must have for anyone using GOG.

That should say one of the lone people left alive...otherwise this is a good list with some decent titles.

======================== If GOG dropped this game here i'd buy it asap....even though I have a copy on original disc somewhere.

============ For poor peeps like me and others these sales are nice, at any rate.

============= Then we could all say "We're commander Shepard, and this is the best store for DRM free"

============
What he said times 10

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I concur 100%

It's a crying shame the series stalled on a cliffhanger in the most recent game, though.

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Someone has to fund that solid gold replica of the USG Ishimura for the dev ceo's desk. :D

More serious answer: They likely want to incentivize people buying it on steam for whatever reason.

You tell me! And to think I still have X Rebirth and X4 Foundations to play!

Any space games list without Descent is incomplete.

Actually it is only the second greatest 4X game of all times. The first one being (of course) Alpha Centauri.

With this out of the way, Stellaris is great!
I didn’t know real-time could work so well for this kind of game without losing the "just one… more… turn" feel. It’s actually quite hard to put a stop to a Stellaris session (despite being able to save at any time), there is always something to do.

It is not a perfect game (only Alpha Centauri is), my three main gripes being:
- a very anticlimatic win/lose screen
- big performance issues during late game (not really tied to hardware)
- an interface that loses a lot in usability on low screen resolutions (I play on a 1280×1024 screen)
Still it is the game I play most these days, and after a couple full playthroughs it still feels fresh. And I’ve not even bought any major expansion yet ;)

Where is Star Control 2 or Origins?!

Ahhh yeah, I did discriminate against ground based 4x games because of the space themed topic but I would rank Alpha Centauri on par with Stellaris. Alpha Centauri is a fantastic game, though its modding doesn't go as deep as Stellaris, which is vastly more modifyable (and also why Stellaris can be ranked so high). Up to the point in which players have full control of the complexities of the game itself, which open up a whole host of possibilities that players can achieve with mods should they feel bored of the base game.

However, the basis of Alpha Centrauris core gameplay mechanics still are extremly well executed, novel while also still standing through the test of time. In a way, Alpha Centauri and Freespace 2 are very similar in these regards.