I have purchased several games since 2011 and now I realize that most of them have a 'Windows Installer 2.0' version (Heroes of M&M 3, Zeus, Total Annihilation, etc.).
Does it mean that most games have been updated?
it is difficult to track new installer versions as only the date of original release is indicated on the website.

Yeah all games pretty much have a version 2 now, if you have the old installer you will find they often have no version number at all something like setup_the_witcher_enhanced_edition.exe or they have a 1 in the name setup_carmageddon_1.0.0.61.exe

I think the main difference with version 2 is that pdf viewers are no longer bundled and it installs to a different location outside of program files because its much easier to deal with permissions that way.

It is quite possible there are other fixes though, it appears that it has been a gradual process of updating the installers for every game in gog's catalogue.

I think I read somewhere that some of the 2.0 installers include game-specific Win8 fixes that weren't in the earlier installers.

ok thank you both of you, really helpful. Time to re download some classics! ok thank you for the info, I hope that GOG will make it easier to see what has been update in the future.

All games that didn't have the 2.0 installer were updated in November to the new installer and part of that was apparently to remove outdated banners in the installer for games that are no longer in the catalogue. Various games were updated to fix bugs or add language packs or other enhancements and there is a thread in the forums called "What did just update?" (yeah, bad English but that's what it is called) which is where people post about updated game packages including GOG folk if you want to track them.

HTH GOG has dropped some hints in threads recently suggesting that they will be providing something in the future that enhances the overall update experience but are not willing to say more about it quite yet other than something like "stay tuned". It'll be interesting to see what they come up with. :)

I guess if they go zero day AAA releases they will provide an update mechanism for games, not just for installers.

You make a good point which I hadn't considered for new games. Yeah, the existing update mechanism is better than it was in the 90s or even in the first half of the last decade, but leaves a lot to be desired compared to say... Steam. Steam seems to have the least painful update experience I've seen so far at least even if it might have some ups and downs itself.

I wonder how they'll manage that without an update client of sorts. I suppose they could integrate better functionality into the existing client and give games the opportunity to hook into the GOG updater or somesuch. Guess we have to wait and find out. :)