Firstly, sorry I'm making another thread even though I made one asking for game suggestions not long ago.
I really just wanted to see or actually test a theory I've had for a while now. Support has been ignorant

I'm beginning to see an increasing number of neglected games, and I have the feeling it has everything to do with how well the game does here on GOG. Blame does not completely fall on the developers, of course; as I believe if a game doesn't do as well as GOG wants it to, it just gets forgotten or put at the back of the list until someone can manually fix it.

Here are some titles I own that I've accidentally found outdated:

Sheltered
Pixel Piracy
Breach and Clear: Deadline
Starpoint gemini 2
Space Rangers: A War Apart
Nuclear Throne (don't own)

How did I come across them accidentally? Well, I was looking through my amazing library when I though 'hey, I might download that again and give it a go'. I cross-check the version with Steam's and realise they are outdated (either by weeks or months), so I get grumpy and look for something else instead. I shouldn't need to go through such motions... I don't care how unpopular these games may be (or whatever the excuse), they shouldn't be distributed here if they're not going to receive proper support.

On a side note - Another instance that reinforces my theory is when the DLC for Dungeons 2 would not register if you didn't have Galaxy installed. I engaged in a lengthy correspondence with support, yet they were adamant that it was my problem and I should just get a refund if I couldn't work it out. But then, someone else voiced the same problem here on the forum, so support ended up fixing it not long after.

In the wake of this, I'll be going through every game that I own that has expected updates. If anyone else has titles they want to bring to light (besides Slender), please do. This way, I'll keep an eye on them too, especially when any sales or GOG connect 'promos' might pop up.

Yep, this is a problem caused by the publisher of the games in not bringing the latest patches for their games to GOG, presumably because they don't give the slightest shit as long as they get people's money:

https://www.gog.com/forum/general/suggestions_wanted_for_gog_mix_games_that_treat_gog_customers_as_second_class_citizens

In general it's a good idea to query that thread and gogmix prior to purchasing games on GOG (on sale or not), but it might be a good idea also to go one step further and make a list of the publishers and developers and boycott all of their products on GOG if any one of their products is not kept up to date with Steam, perhaps giving them a maximum one month leeway to avoid getting on the list. One month is a HUGE amount of leeway IMHO, but I'm willing to give them that much because I'm a generous customer towards publishers.

Furthermore, if a publisher does not update their game to the latest patch on GOG within 3 months to bring it in line with Steam, then I personally would prefer to see GOG halt sales of that game and/or pull the game and/or publisher from the store completely, as they are selling a defective product without doing the best they can do to rectify the situation as soon as possible. Not that GOG would likely do this mind you, but IMHO they *should* do this because selling known broken games with known fixes and not making them available here also is a massive disservice to our community.

I tend to add to it most of the time :p
Problem is, with all of the games I own, I usually buy them the moment they appear here. So, consulting Fronzel's mix can't apply for day-1 games.

Your last sentence couldn't be said better, and I agree completely.

As much as I agree with you, I do remember some publishers claimed there are issues with updating Gog versions,
Some are frameworks issues (Galaxy [api?] isn't yet adept enough to be used as an automated push method like on Steam),
Some dependent on in-built features non yet existent (there are claims of Steam having an issues investigator for developers),
Others are just using Steam's client and api as workarounds and codependent on stuff that are only found on Steam...

So obviously any game sold here should get updates on par as steam, but for the newer titles, I'll give some* developers some benefit of the doubt until Galaxy (and other related framework) functionality gets dealt properly.

* This list SHOULD NOT contain Telltale(and Gothic to some extent), as they have definitely reached abusive levels on some titles.