Just gonna list out a bunch in no particular order:
Sacred
Arcanum
Leisure Suite Larry Series
Escape from Monkey Island Series
Planescape: Torment
Interstate 76'
Deus Ex
Vampire The Masquerade: Bloodlines
Beyond Good and Evil
Grim Fandango
Elder Scrolls: Arena
Elder Scrolls 2: Daggerfall
Full Throttle
Little Big Adventure
LBA 2: Twinsen's Odyssey
Sanitarium
Longest Journey
Baldur's Gate + Expansion
Baldur's Gate 2 + Expansion
Xcom: UFO Defense
Nox
Armed and Dangerous

Add me to the list of freaks who want to have Riven and Exile on the hard drive of my Vista machine.

I'll also add to the list for Red Baron 3D provided it came with a Glide wrapper that actually works well!

I vote for the original Magic: The Gathering game. The one with Shandalar.
Only... Wizards of the coast is like the EA of card games... the day they share/give/sell rights to anything will be a cold day in hell indeed.
Also, Transport Tycoon and Railroad Tycoon need not be on the list, seeing as both are abandonware, and thus are easily found free, legally, on the internet and at least Transport Tycoon works just as well as it ever did.

I would love (and most certainly would buy) these games on GOG:
Duke Nukem Series!
Pizza Syndicate! (or "Fast Food Tycoon", that was it's title when published in USA)

Going to second all the Lucas Arts games listed; Full Throttle, Grim Fandango, and so forth. Also Sanitarium and Magic: Duel of the Planeswalkers. I dunno if anyone mentioned these yet (sorry! Haven't finished the thread.), but The Neverhood, Arcanum, and System Shock 2 would be neat. Oh, and Beneath a Steel Sky. Actually, there are lots of old Sierra adventure games that'd be great...and that King's Quest Collection got marked down pretty heavy, you guys might even be able to swing that...
IN SUMMATION: Every adventure game ever, please!

Well I was trying to make a combined list of all the requests here but I got to 297 unique games at the end of the 4th page... Might take some time :)
Karl

If you publish System Shock 2 and make it working on Vista, you will become absolute Gods! ;)

My list:
Planescape: Torment
Baldur's Gate I & II
Icewind Dale
System Shock I & II
Deus Ex I & II
Max Payne I & II
and also...
Planescape: Torment again :)
....
....
Did I mention Planescape: Torment?
Ciao

I'd like to put in my two cents if I may ....
Ultima Underworld I & II

Grand Prix 1 and 2 by Microprose. The best Formula 1 games ever. In fact, I'd like all games made/published by Microprose. Their flight sims, RPG's, the lot.
The Bullfrog games!. Theme Hospital, Theme Park, Dungeon Keeper, Syndicate... Bring them here!
Every 2d point 'n click adventure game you can find. They don't make those anymore, but I still want them! Haven't played them all yet and besides DosBOX you might also use ScummVM.
Delta Force 1 & 2. Just because of the memories. Especially multiplayer!
The General series. Panzer General, Fantasy General, Allied, Pacific, Star. Would make a great package!
Terra Nova Strike Force Centauri. One of the first tactical, squad-based FPS.
That's about it. I would also like to put in another vote for Planescape Torment. I missed it the first time around and I regret it!

From my loooong list:
- Crusader: No Remorse
- Crusader: No Regret
- Little Big Adventure 1 & 2 (a.k.a. Twinsens Odyssey)
- 'Tex Murphy' series (from "Mean Streets" to "Overseer")
- all Discworld games
- all Monkey Island series
- Frontier: First Encounters (almost forgot ;)

Myst (or more precisely, realMyst)
Riven
I've been replaying the Myst series recently but had no luck getting these two to work. Would love to be play the complete series again.

Transport Tycoon is not abandonware. You can buy it easily here in aussieland (deluxe version)

Well, I glanced around a bit and saw my wishes pretty much covered already, but since I didn't see any rules on the first page it can't hurt to re-iterate them I guess.
Definitely a big vote for the Bullfrog games, especially Syndicate. I can get my old copy to run, barely, in DOSBox, but no sound and a lot of graphical bugs still occur. Populus 2 is another one I recall really enjoying, and I don't even have my CD of that anymore sadly.
The original X-COM, and some of the sequels, and the Lucasarts original X-Wing and TIE Fighter games (CD-ROM collectors versions are what I originally owned). Some of my favorite original computer games, and, along with Populus, the only ones I've lost the CDs for. And while I have the CD still, if you can do anything to improve Rebellion's stability on newer systems I'd definitely repurchase that one ;)
Space Quest stuff would be nice too, I only ever got to play the 6th one.
tl;dr list format:
Lucasarts:
X-Wing
TIE Fighter
Star Wars Rebellion
Sierra:
Space Quest series
Bullfrog (by way of EA)
Syndicate Series
Populous Series
Microprose
X-COM Series
Maxis
SimCity 2000
SimAnt
Alliance Interactive (or Three-Sixty Pacific)
Harpoon series