Baldur's Gate 1 and 2, hands down.

The title is not misspelled. It's "Caesar" :)

omfg does anyone clean that list Metal Gear Solid 4 should not be on it lol not old, not even pc, ps exclusive wtf they except you to port it and buy the rights for it?

Grim Fandango, System Shock 1&2, Full Throttle, Monkey Island Series

Red Faction 1
Some of the best MP ever!!

That's what I said. You even quoted it. "Caesar" is the correct spelling; the misspelled titles should be removed to avoid splitting the vote.
Also, searching by the correct spelling brings up both listings, but searching by the incorrect spelling only brings up the incorrect one.

I never played System Shock 2 somehow, and I REALLY want to. Like... REALLY.
The rest of my list is the same as the top ten on the dedicated page really, plus some more Lucasarts titles and some classic shooters. I would LOVE to see Sam & Max or the early Elder Scrolls games, Arena and Daggerfall.

I'm gonna throw some publishers' names on the pile here:
Lucasarts
All the SCUMM-based adventure titles; Monkey Island, Sam & Max, Full Throttle, etc.
Grim Fandango...
X-Wing series, perhaps?
Maybe even Rogue Squadron 3D, which was quite fun on the PC.
And of course (guilty pleasure alert) Star Wars Episode One: Racer. Yeah, laugh it up.
...although maybe the Star Wars license could be tricky in terms of copyrights.
Eidos
The Legacy of Kain series, although I'd be happy with just Soul Reaver.
The early Tomb Raider titles, perhaps?
Can't go wrong with Deus Ex.
How about the Thief series?
Or even Anachronox?
And my personal favorite, Omikron: The Nomad Soul, AKA "That David Bowie Game."
There's a lot of potential there. Does Eidos have some sort of exclusivity agreement with Steam or something?
Acclaim
A shameless personal addition, just because I want to play Re-Volt again.
Ubisoft
Another personal one. Just give me Rayman 2 and everything else is gravy.
And last but not least - and bear with me here:
Atari
Yes, the modern-day Atari. The Atari that published The Witcher. Surely there's a relationship already in place, and there's a fair amount of great Infogrames (remember them?) IP languishing in archives at Atari that needs to be revealed to the world once again, not the least of which being Outcast, which I am still playing and for which I would kill to have a compatibility update.
Independence War 2, anyone?
Or maybe the early Alone in the Dark titles?
There we go. That's about all I got. Enough wall-o'-text for ya? ;)
NINJA EDIT: BBCode didn't like my italics. You got something against expressive typists?

Ya, sorry, I've read your post without using my brain. :)
Anyway, Caesar series and another similar games (Zeus: Master of Olympus, Pharaoh and Emperor: Rise of the Middle Kingdom) are worth being available from GOG.

i thought about...
Final Fantasy 7 & 8!
with XP & Vista compatibility...
that would be perfect.

I admit I could have phrased it better. And yes, those games would be great to have available. :)

I'd really love to see the original Blood Omen on here; never could get the PC version to work. Another vote for the Lucasarts games too, especially Grim Fandango.

On top of my list are:
Blood
Blood 2 + Expansion
Jeff Wayne's War of the Worlds
Lords of the Realm II + Expansion

I'd luv it if GOG had the Wing Commander Series games!!!

Everything from the Close Combat series by Atomic Games (first two or three games published by Microsoft, later games by other publishers).
Panzer General series, by SSI. I would also happily pay a few $ per game to download other old strategy games from publishers like SSI.