I don't know about "forgotten" but sooner or later I'd definitely like to see:

Albion (!)
Al-Qadim: The Genies Curse
Anachronox (curious about it)
Anvil of Dawn
Blood Omen: Legacy of Kain (ok, not really a RPG, but Al-Qadim isn't either ;) )
Dark Sun 1 & 2
Dark Messiah of Might & Magic
Dungeon Hack
Eye of the Beholder 1 & 2
Forgotten Realms Unlimited Adventures
Grandia II
Knights of the Old Republic (with full Vista-compatibility)
Rage of Mages 1 & 2
Ravenloft 1 & 2
Silver
System Shock 1 & 2 (curious baout them)
VtM: Bloodlines
The Wheel of Time (might not be a real RPG but I'm curious about it)

And maybe also:

Dungeon Master 1 & 2, plus Chaos Strikes Back (classic, but there's also the free RTC)
Evil Islands (curious about it, is it any good ?)
Eye of the Beholder 3 (not as good as 1 & 2 but still enjoyable enough)
Fable (curious about it)
Hexplore (curious about it)
Menzoberranzan (I think I read it's a buggy mess)
Prince of Qin (sounds interesting but I read a few bad things about it)
Revenant (not sure I'd want to replay it)
Throne of Darkness (I still own the retail and it works fine, never played through it though)
Wizardry series (never played any of it but I probably should try them)


Aaaand ....
someone should port Chrono Trigger and Vagrant Story to the PC and then sell them on GOG. ;)