I think gog has always tried to target releases that have "cult" followings. So really too many to name, probably at least half of gog's releases.

Planescape Torment has already been mentioned, and probably is the picture in the encyclopedia next to "cult game." :)

But yeah, a lot of the games on GOG have cult followings of some sort or another. Rather than listing them, it might be easier to compile a short list of games with the heading "We don't think these games ARE cult, why did you release them GOG?" ;)

I would argue that Anachronox might rival that place...

Alpha centauri