Well, I think GOG should contact Kalypso to release SM on here. But maybe Kalypso is not interested to release some of its titles on GOG.
GOG really needs to add more non-FPS titles to shooter category.

My most wanted Shmup that is available on Steam is Raiden IV.

Is there a reason why these games are not released on GoG.com?

It's questionable how well-known Raiden is outside of Japan :p

The people working at GOG are not fans of the genre, and have made it clear they don't want to support niche titles unless it's a niche that's currently in vogue. So every programmer-art roguelike under the sun gets a release while shmups from long-established companies that have been released on several platforms get shafted.

[citation needed]

The publisher of Raiden IV has only just shown up on GOG publisher listings, so this one might not be far off.

Mushihimesama was rejected by GOG despite coming from the largest and most respected company still currently making shmups because "it doesn't seem well known outside of Japan" (as if any of the indie games released here are "well known" before they're released and given a chance to prove themselves) and they've also rejected games from Triangle Service for similar reasons. You can even see this earlier in the thread, directly from the publisher.

It has 215 votes on the community wishlist.

Undertale has nearly 1000.

Touhou has a mild HANDFUL of votes.

[spoiler]

Spoiler: It's niche.

[/spoiler]


...Also, most Shmups are Japanese, and dealing with Japanese companies tends to be a complete [expletive deleted].

Where's your point? Undertale isn't a shmup, so no need to compare them. It just uses some shmup elements. It's absolutely not about perfecting your gameplay, awesome detailed bullet patters, dedicated construction of every stage and competing for highscores.
Almost no one votes for Touhou because most people who like them know that ZUN doesn't want them localized. Be it because he fears for it's doujin scene by giving IP rights to others or because he just doesn't care for the west.
The game isn't niche. It's part of the most well knows shmups, assuming you care for the genre at all. Shmups by themself may be a small genre compared to RPGs or FPSs, but so are Beat 'Em Ups or Dungeon Crawler. Does this mean you shouldn't release good games of these genres?
And CAVE is the most famous and well known shmup dev nowadays. Declining them is a big middle finger to all GOG users who like shmups.
Except that Degica already asked to have it released. It's GOG who's a dick here.

All the shmups I posted in the OP, as noted in the OP, are simply waiting for GOG to say yes. Degica & Nyu between them have quite a lot of shmups that could be on GOG right now (even more then I posted) if GOG were willing. I wouldn't be surprised if there were other shmup publishers who've been turned down too.

Nuclear Throne currently has 54 votes and it's already in the Upcoming Games tab. The wish list is a nice feature for the relatively few games that are in extremely high demand, but it means little for GOG releases of everything else.

I think andysheets is right here. The recently released The Moment of Silence only had 167. Fallen Enchantress, even if you add up all the entries for it, still comes in at less than 200. Outside of those titles with crazy demand behind them, the wishlist probably isn't the most accurate metric, or at least isn't the only indicator of what should be considered too niche.

I'm aware it's niche. That's why I said "GOG has no interest in niche genres they don't personally enjoy." I never claimed it wasn't niche, so I'm not sure what you think you're refuting.

That said, GOG has plenty of niche titles. Selling DOS games in the Windows XP and up era, prior to GOG making a thing out of it, was a niche, and that was their entire business. And given the absolute runaway success of Undertale, a game with a fifth of the hype should still do more than well enough to fit in with all the other indies here (or, like others pointed out, it's a sign that the wishlist is a mostly-unknown feature and isn't used enough to be any kind of accurate measure for popularity).

As for working with Japanese companies, if you've read the thread at all, you'd know that those are already working through a western publisher called Degica (Degica are actually the ones who made that Mushihimesama wishlist entry), and both the Japanese developers and the western publisher want to put the games, DRM-free, on GOG. And besides... it's not like GOG is against working with Japanese developers, even indie ones, because they have plenty of games from Japan.

It just boggles my mind that a site built on selling indies and old PC games is using "it's not popular enough" as an excuse.

I agree that GOG could use more shmups but I don't really care that much anymore either. GOG has lost me on waiting for them to get games released, I just buy them on Steam if I want them.

Believe you me, that one you don't want to see on GOG :) (different tastes and all, but somebody had to say it :))

Now that's off my chest... I personally don't care whether GOG or somebody else releases the games, as long as I get a game.zip or setup.exe. If you share the sentiment do let the developers/distributors know. I've had some nice chats with folks from Nyu and Fruitbat Factory about this in the past, followed by non-Steam non-GOG releases that I happily bought. Apparently Degica is considering the Humble Store now, so hopefully all will end well.

PS. I had a good chuckle over this one from the Mushihimesama Wikipedia entry:

"The PC version holds an aggregate score of 92/100 on Metacritic, making it the fourth highest-rated PC game of 2015"