What are the "best" or "most highly regarded" games you own but you have not yet played, and why the heck haven't you played them?

Mine would probably include:
* The Witcher
* Deus Ex
* Planescape Torment
* Fallout 1 and 2
* Baldur's Gate 2

I have owned some since I joined but just not gotten round to installing them yet... Personally, I am enjoying playing through my older games first (currently Betrayal at Krondor) and then maybe I will move on to some more modern RPGs.

The D&D rpg series here on GOG. Since I bought them last year I haven't got the time to play them.

Dishonored, deus ex human revolution.

Will start Dishonorerd soon.
Haven't got to deus ex due to huge backlog, but i think it will be next on the list when i am finished with some i'm playing now and when i am around half of dishonored.

The Witcher
Starcraft 2
A lot stuff on Wii and Nds (Zelda, Pokemon...)

Theme Hospital. I've been busy playing other games but soon I will play Theme Hospital.

I can't really say they are the best since I haven't played it yet. But I read and watched some gameplay review so the reason I buy them.

Here in GOG:
Heroes of Annihilated Empire, Cossacks Anthology, Cryostasis, Riddick, Total Annihilations, Arcanum.

The reasons: I still have other games, rpg and most open world games (GTA4, Skyrim, Bladurs Gate 2, DE 3, etc installed in my system. and I don't have 100% free time to finish them all.

Portal 2
Mass Effect
L4D 1 and 2
Witcher 1 and 2
New Vegas
BG2

>.> That's not even 1/10th of the games I have but haven't played.

Hard to say which is best if you did not play it but there are a few which people say good things about:

Baldur's Gate 2
Icewind Dale 1&2
Portal 2
Arma II
Spec Ops The Line
Saints Row The Third
Dawn of War II
The Guild

and many many more. Darkadia says my pile of shame (games unplayed, expansions included in the count) is 380. Plenty of those 380 are very good games.

Edit: Adding Sacrifice just for kicks :P

http://darkadia.com/member/Aningan/library#!/shelf/owned/unplayed/1

Fallout 2
Gabriel Knight 1

Best games you own but have not played (properly) as they deserved?

King of the dragon pass and Darklands.

Both are the greatest games on GOG but i can't concentrate long enough. Yeah, i am broken - in the Kitten mode for last 7 years.

I have not heard of Darkadia. It looks prettier than backloggery, which is what I use... I don't know if I can move my stuff over though

Took a few days to get stuff from backloggery to darkadia, but that's what wasting time at work is for :))

Wing Commander Privateer
Quest for glory 1-5
Wizardry 1-7
S.T.A.L.K.E.R. Shadow of Chernobyl
Stronghold
X-com Terror from the deep
Eye of the Beholder 3
Combat Mission II: Barbarossa to Berlin
Hitman: Contracts
Sherlock Holmes vs. Jack the Ripper
Space Quest 2-5
Achtung Panzer: Operation Star
MechWarrior 3 (can't get it to work)
Blackwell Deception
Trine 2
Geneforge 2-5

For many of them I've just not been "in the mood". For Trine 2, I'm waiting for another person to beat Trine 1, so that we can play it together.
As it shows pictures of all games, how does it handle games not in its database? I have a few games that I'm pretty sure are not in it.

The Witcher 2. Bought it on day one, the poster is hanging on the wall, papercrafts patrol the desk, and the game is waiting for a rig that can run it. ;)

The database is the one from Giant Bomb. There were a couple of games I had that there were not in the database. So I just made a Giant Bomb account and added them myself. Or a game did not have a picture so I added that myself. Took like half a day to have the changes approved.

Word of advice: if you do decide to add games on Giant Bomb don't add details unless you add them in your own words. I added a very short two line description of a game, the one from the developers, and they hit me with a warning for plagiarizing. Meh... if they'd rather keep it empty than have the developer's own description... whatever.