Sadly, the online GOG community is pretty much non-existent, right now. I have
Dying Light,
Torchlight II,
Victor Vran,
Titan Quest,
Grim Dawn,
The Last Blade,
Metal Slug (plus
X and
3),
Hammerwatch,
Worms Armageddon,
Worms World Party Remastered,
River City Ransom: Underground and a few more (I won't list the ones I have uninstalled :P ), but almost no one is playing them whenever I try joining a lobby. I guess the "anti-online" feeling prevalent here on GOG is just too strong for us to have any sort of sustainable online community. I heard
Absolver will have cross-play between Galaxy and Steam, and I sincerely hope that's the case, because if it's GOG-only, it's going to be pretty much dead on arrival (especially considering it relies *a lot* on the multiplayer/online aspect)...
When GOG started introducing dedicated servers and Galaxy online play, a decent amount of people were playing
Aliens vs. Predator Classic 2000 (and even the sub-par
Double Dragon Trilogy), especially during server stress tests, but those numbers went down and keep getting lower each passing day.
Your best bet is to just get some older game that works with something like
GameRanger, such as
Nox or
FlatOut 2, and play them online using the program, if you ask me.