Quest for Glory 1 was remade by Sierra, and is not available for download legally.
King's Quest 3 was remade freeware by
Infamous Adventures, and they are also working on Space Quest 2, which is in the bug-squishing phase (unfortunately that takes a long time!).
The quest for glory series are one of my favourites, I always played as a mage the first time through, then completed them in various other ways. Quite a good amount of replay value.
I actually recently did a review for Quest For Glory IV for Abandonia, although it's not been uploaded yet.
QFG4 had full voice acting for the CD version (For the anthology certainly, not sure if it was available for other versions), and starred a couple of interesting persons...
IMDB linky! I should probably add that the rights are held by Vivendi international (the company that owns Activision/Blizzard). They approved the AGD interactive remakes, but I'm not sure what their opinion of selling them through GOG would be. I'd hope a deal could be made, but who knows?