Can anyone think of some old school PC RPGs like Baldur's Gate and Fallout that's not currently available on GoG? I'm wondering if I should hold out for something that might be released in the future, or just get an RPG title that's already in GoG's selection.

I think they probably already have the best of the 90's stuff, unless I'm forgetting something. Nox would be cool, never got to play that one :[ They'd probably have to go back further and dig up the old RPGs like Ishar and Might & Magic, though I don't know how many of those are left to get either. Still hoping we might see the SSI Gold box games :D

Wizardry, Wizardry, Wizardry annnd Wizardry.

You can throw in Thunderscape too if you want and Dark Sun 1&2.

Ultima series

Lands of Lore, SSI crpgs, Albion, Daggerfall, Dungeon Master.

Well one of them had a pretty serious late game bug i think. I love the setting though, very Planescapey, shame that the setting was never used for another crpg.

I'd like to see more games from late 80's to the mid 90's. Like the Eye of the Beholder series, Dungeon Master, etc.

Is there a PC version of Black Crypt, the Amiga game? And Ambermoon?

Already on GoG

Morrowind.
Some of the Final Fantasy wouldn't hurt.

True, they probably have the best of the best already but there's still lots of interesting old RPGs that could be added, some of them already mentioned, like all the SSI games (I'd like to see especially the two Dark Sun and the two Ravenloft titles, plus Forgotten Realms Unlimited Adventures, and Al-Qadim, if that still counts as RPG), Lands of Lore (especially Pt. 1, The Throne of Chaos), the Eye of the Beholder series, Anvil of Dawn, maybe Dungeon Hack, definitely Albion, Nox, maybe Revenant and Silver, why not Diablo or Throne of Darkness - the new breed of A-RPG disliked by some but still not bad games at all (I guess Diablo will never happen though).

Oh, and how could I forget the Ultima series and Ultima Underworld!?

The CD versions of Arena and Daggerfall as legal freebies already set up to work with modern Windows/DOSBox would be cool, too (Bethesda only distributes them as is - and maybe even with some videos and speech missing? - without any help on setting them up and curiously without manuals).

Do Deus Ex and System Shock count as RPGs?

BTW, everyone wishing for Dungeon Master might want to check out this excellent freeware clone:

Dungeon Master - Return to Chaos (RTC), a faithful freeware clone of FTL's first person RPGs Dungeon Master (1987), the expansion Chaos Strikes Back (1989) and Dungeon Master II: The Legend of Skullkeep (1993), including a RTC custom version and a level editor. Runs under Windows.

I still wonder why the Wizardry series isn't here. It was a Sir-Tech product, no? Or is this something D.W. Bradley has to approve of first?

GOOOOOOOLLLLLD BOOOOOOOXXXX!!!!

Deus Ex, Ultima series, Thief series. Gold box was very cool back in the day and would be nice, but I can live with it just as a memory.

All of the above.

Plus:

Titan Quest Gold
Depths of Peril
Quest for Glory series

As far as Ambermoon goes.. sadly no. Only it's predecessor Amberstar managed to get a PC port. Thallion had to close partly due to the rampant piracy problems, before they could port it or even develop the third part of the "Amber" triology. At least some of them got new jobs at Blue Byte and developed the really great Albion there.