It may have been mentioned somewhere in the last 200 pages, but if so, it bears repeating: Binding of Isaac.

Remember to explain the issue. Is it missing a version, a DLC, voiced narration by Eric Idle that's only on the Steam version?

Yep, post 3980.

It seems that the soundtrack of 'BPM: BULLETS PER MINUTE' is missing one track compared to the steam version, according to a review.
The descriptions on the pages of the soundtrack seem to confirm this.

https://www.gog.com/en/game/bpm_bullets_per_minute_soundtrack

Sorry, I should have specified - it's been covered pretty thoroughly in the Isaac forums already (it's most of the front page at least), but basically the game cannot be 100% completed at this moment due to certain achievements tied to Daily Runs being inaccessible to players, among numerous other things. [[EDIT: It's not most of the front page, but it's most of the recent threads. The Isaac forums are a bit dusty from departing souls and sadness]]

My only real concern is I'd love to get the balance changes the newest patch offers, and don't even really care about getting 100% as I prefer to play completely offline. There's only about seven games I play anymore and I've been migrating off Steam for awhile slowly but surely, and Isaac is one of those games. I have no plans to use Galaxy so the online stuff for Isaac doesn't concern me quite as much, but I feel for other players on other platforms besides Steam who would like the newest patch.

People have tried reaching out to GoG and Nicalis, but we've either gotten extremely vague answers or no reply at all. I understand if it's company policy not to inform us of developing talks between a dev and GoG, but it'll be a year in November that GoG has carried the outdated Isaac. I've heard that Nicalis has more or less called it quits on Isaac and if that's true, that's sad but understandable... but we would really appreciate getting this latest patch for GoG as well as all the consoles that are also out of date.

Yeah, they're a terrible publisher, whose record of abandoning projects or otherwise ghosting devs.

And pulling an Elorg on Pixel; ensuring that most of the ports of Cave Story don't actually give money to Pixel.

It's always worth to wait some time before posting.
Not many days release updates the same day on all platforms. If the difference was a month or more ... well, then it's probably worth putting it on the list.

A delay is a delay, and makes it second class treatment and at least worth a notification. As for actually putting it clearly on the list, a week should be enough.

Think it's time to add GORD to the list. The game has received multiple updates on steam and not one on GOG. No reply from the developers on discord as when the GOG version will be updated. Honestly seems like there working on updating the Consoles version right now. I don't mind waiting, but you think updating the GOG version would be easy, compared to the consoles version.

On Steam Monolith has been renamed to "Star of Providence", updated and the DLC has been included into the main game. Not on GOG

Other than the name change, the game doesn't seem to be missing any bugfixes or content updates as far as I can tell from the game's Steam update history posts.

Is the GOG version not the 2020 Relics of the Past update? According to steamdb there have been 6 updates in 2023. And the DLC is missing from the GOG version without question and still sold separately in the GOG store while on Steam it says "The game now comes with the previously paid DLC, Relics of the Past, for free". And from the name change announcement in June: "Once the name change rolls out sometime in the next month, we will also be making Relics of the Past the default version of the game—the base game will cost $15 and the DLC will be included".

Found this, and now I wonder if the Steam version is getting beta fixes:

https://steamcommunity.com/app/603960/discussions/0/3815165632071613498/

I see what you're talking about now, given the steamdb has an update that lines up with that forum post. Seems they're getting beta fixes. Hopefully the devs are just waiting for all bugfixes before pushing the update to gog, and not abandoning the gog version altogether, though i'm probably holding false hope here given all the other games having fixes and updates abandoned on gog.

Update on Urbek City Builder DLC. When asked if the DLC is coming.
Develops said the in medium term they don't thinks so

The Bard's Tale: Remastered and Resnarkled is finally here and can be removed from the list. Going to keep both versions backed up as the original release was overwritten by this.

Another off of my list, no matter how slowly is still good. There are more than a few that I have no hope for though after all this time.