Reading the 90's giveaway thread got me thinking about some games that are highly acclaimed that I've never played. My console gaming days largely ended with the Sega Genesis / Mega Drive, so there are lots of console exclusives that I have never played. When it comes to PC games, I have a few notables that I have never played:

Half-Life - This is the game that started me thinking about this. There have been boatloads of praise heaped on Half-Life, often calling it the greatest FPS ever etc. I've got a couple hours into Half-Life 2, but I've never played Half-Life. No real reason other than the fact that FPS's aren't my favorite genre. That isn't really enough though - I've played and enjoyed lots of FPS's.

Diablo 2 - This is a funny one, because I played the first Diablo a lot. I really enjoyed the first Diablo. For some reason, I never justified the money to play the second one.

Starcraft - Another Blizzard title. At the time Blizzard could kind of do no wrong. I was a big Blizzard fan. I loved Warcraft II. Despite all this, I never bought Starcraft.

Grim Fandango - I never really new what the game was about. The title and the cover art just never called out to me to buy it. I've still never read a review of it, which is strange, because I like adventure games.

I'm sure there's more, but these are the first ones that come to mind.

Any big games you've never played?

Witcher

Half-Life 2 - and, tbh, I don't know why, because I loved first Half-Life. Somehow never picked it up. But, as I heard, its ending (I mean ep2) is big cliffhanger so maybe it's for the better. :)

Grim Fandango - more or less same thing as OP.

Monkey Island series - again, I have no idea how I missed it, but I will try to play it in the future. :)

Paying with your very soul would be justified for this game. :D

Diablo II- I have only played Diablo III on the PS3 per my daughters request, and we had a lot of fun with it. From what I've read the second one is the superior one, but I always find something else to play it seems.

Any Fallout game (besides 3)- Never even heard of Fallout until the #3 game out. I even pre ordered the game when I read about it. I have attempted the game 4 times and can't get past playing around 2-3 hours. I find it drab and uninviting and it turns me off from wanting to try any of the other ones.

Well, most ppl consider 3 the worst in the series (me including :P) so it can only get better with others I guess.

I have Fallout New Vegas but have never tried it, maybe one day I'll attempt it.

Lots. I won't be including stuff from the neverending franchises that are mainly for consoles (Legend of Zelda, Final Fantasy, Mario) since I doubt I'd ever play them.

For PC, off the top of my head: Deus Ex, Fallout, Diablo and its sequels, Dungeon Keeper series. These are the ones I have and plan to play soon. I might also get and play the original Grim Fandango.

I haven't played lots of adventure games, because I don't like the genre. I also don't play much MMORPGs so I missed WoW and the like.

Ditto for Diablo 3.

There are loads for me...

Any Adventure games.. Monkey Island, Grim Fandango.. I think I've probably played a few minutes of Monkey Island at one point or another but I've never been much of a fan of adventure games so haven't properly played many games in the genre.

Baldurs Gate 1 & 2 - I missed all the D & D based RPGs when they came out and haven't gotten into them properly since finding GoG.

Final Fantasy 7 - One of the few FF games I've never really played for any significant time. Missed out due to never owning a Playstation.

The Last of Us - Don't own a playstation, not a fan of horror games.

Resident Evil 4 - See above.

Any Grand Theft Auto after 3. Played a bit of whichever was released after 3 and didn't really like it, haven't seen or heard anything since to convince me to give the series another go.

I'm sure there are loads of others too...

Oh God SO many games sitting in my 'to play' list
Witcher Series
STALKER series
NWN Series
Vampire: Bloodlines
Arcanum
Batman: Arkham series
Fallout besides the first one
Elder Scrolls besides the first one (and a bit of Battlespire and Redgard, I guess)
Wastland series
Ultima series (properly - tried to get into 0 and 4 but failed)
Might and Magic
HoMM
X-Com besides the first one
..and that's just some of the ones I own from the top of my head!

Every highly acclaimed console game, since I've never had any console.
Since my parents tried their best to completely shelter me from videogames when I was a kid, there are LOTS of good games I've never even heared of.

Grim Fandango - I've never even heared of it, until it took lead in GOG wishlist.
Fallout - first I heared of it when Fallout 3 came out, and since I'm not into shooters at all, I completely ignored it. When I saw the originals on GOG, I was still uninterested, because the setting is just not my cup of tea. I got it when it was free, and I still haven't played it.
Planescape Torment - First heared of it after I joined GOG. Still haven't played it.
Deus Ex - The setting is not my cup of tea =/
Ultima Games - Again, never even heared of them before GOG.

And there are many highly acclaimed games I've never played, simply because they belong to a genre I have no intrest in (like shooters or horror games)

I guess I shouldn't complain. Could have been Baulder...

Never ever played at all or only taken a short peek at them so far?

There are so many, and especially when it comes to console exclusives, I didn't play a lot of them. Games I might have given a try if there were digital downloads for PC include Uncharted series, Halo, Heavy Rain, Beyond: Two Souls and The Last of Us, Little Big Planet series.

Then there are those classic PC games I never had a chance of playing and that I do hope will come to GOG one day, like the Noone Lives Forever series or The Neverhood.

I've also never played a Call of Duty, Counter Strike, Splinter Cell or Metal Gear game, but that's because in general I'm not interested in military shooters or semi-realistic spy and stealth games at all. And of course there are lots of other big titles I never tried because I'm not that into their genre, mostly strategy, simulation games and JRPGs (so no Final Fantasy either).

Games that do interest me to an extent and that I've checked out for a bit but never really got into them so far despite their popularity include the Witcher series, Deus Ex series, Thief series, System Shock series, Ultima series, Fallout series, Knights of the Old Republic series (or any Star Wars game), Dragon Age series, Assassin's Creed series, GTA series etc. And on the PS2: ICO, Shadow of the Colossus, Okami and God of War (I like them but didn't get very far compared to their gamelength).