How about this one!
"Labyrinth" - 1986
Back then I came close to finishing it but never did.
So I am trying my hardest... it's old and tedious and hasn't the best control system but I am giving it ago.

Does it work with DosBox on Vista? I still have the original CD, and I remember not being able to get it working with some program of the sort. Maybe I'll try again.

Also, the Manhunter games, Conquests of Camelot, and The Last Express.

Cruise for a Corpse. I was hopeless at it as a kid and despite liking the idea of it, never went back to finish it.

It definitely works with DOSBox. If you try getting it to work and run into problems, just post in the Tech support forum, and I'm sure someone will be able to help.

Yeah I remember that game.... I think I was on the same boat as you
(no pun intended...HA!). I was not very good at it but enjoyed trying to play it.
It was one of the first decent games released by Delphine Software in 1991.
Of course It was soon forgotten when Another World & Flashback came out but I would still like to give it a go... might be able to finish this time round.

Oldest would have to be most of the games from Lost Treasures of Infocom (I've beaten about 4 of the batch of 20+). I'm just going to use walkthroughs for most of them, might attempt a couple without one.

Graphical there is Quest for Glory 1 (on the collection I've owned for 12 years and hardly played) and Police Quest 2 (also have owned the collection for 12 years or so).

Haha, I own this as well. It seems too random to try to waste time with without a walkthrough, but maybe I will someday. I did try it with a walkthrough in like 1998, but eventually got tripped up somehow and never finished.

I literally just played that part last night. I have a good brain for sound, so I was able to get that code right away after only watching the video once.

Yes, same here with Cruise! I remember there being some insanely difficult puzzle...

I still haven't finished keepsake. But I really want to. I keep getting distracted by other games though.

I did however finish dracula path of the dragon a couple of weeks ago where my first save game was august 2009, and I also just finished Nostradamus, where I'd left it since 2008. I've also got Darkfall the journal, where my save game is dated april 2007, but can't really see myself getting stuck into that game any time soon if ever.

The oldest adventure game I gave up on was Infocom's ultra-challenging Spellbreaker. I believe it was the last Infocom game I even played, back in 1985.

More recently, I tried my hand at The Black Cauldron, and got pretty far before I got fed up with being repeatedly killed and abandoned it. Maybe one day I'll revisit it and finish it, because I actually liked most of the game quite a bit.

would have to be loom for me. I enjoyed the game, but i got distracted and bored with it. I should probably give it another try sometime.

Too many to list!

The original Alone in the Dark and Sierra's Inca II (the action bits of both were too much for me).

Hrmm... There were a few really awful ones I didn't play for more than a couple hours before abandoning (Nightlong, 7 Games of the Soul, Temujin, others I'm forgetting right now).

Believe it or not, I never finished the Longest Journey; totally hated it.

Finally, I'm another non-Keepsake-finisher.. there were aspects I loved (Zac as the wolf, the 'gentle' nature of the story, the mystery aspect), but I got tired of the endless, non-plot-related 'puzzle box'-type puzzles.. I felt like I was playing a less-interesting Seventh Guest, or maybe even a late Myst clone.

I think you should definitely give it a chance. I've tried to play it after I've played "The Lost Crown", but I couldn't force myself to look at it, as it does look rather bad on nowdays PC monitors. But, I've finally installed it couple of days ago and finished it yesterday. I must say that I'm glad that I've once more passed "don't judge the book by its covers" test, which was also the case with TLC. I remember, that when I saw grey skies / blue grass, following by Nigel's duck-walk, I said to myself: nah, it seems I'll skip this one. But when I've started to play the game, I've learned an important lesson, which importance I've confirmed again by playing "Dark Fall: The Journal".

A few words about the game itself. Now that I've finished it, I can concure with the reviews which emphasizes the "labour of love" factor when talking about DF: TJ. You can definitely feel this when playing the game. Like all Boakes games so far, it shines the most when it comes to story and atmosphere, but it also features a lot of interesting and well-thought puzzless. Technically, this game is certainly ruff for today's standards, but this don't affect it's artistic value.

All in all, I think that I will now finally finish "Dark Fall: Light's Out" too. ;)

It would probably be the Tex Murphy games, or "Mean Streets"...since I haven't gotten past that one. I just didn't know how to control the transportation, and it just seemed overwhelming at the time.

I had that problem as well when I first tried Mean Streets. It turns out to be pretty easy because I believe you can just set the coordinates and put it on auto-pilot and sit and wait while it drives for you. It's a fun game, not as arcane as it seems it would be with that transportation system.

I may have to try it again, since it is a classic. I was just never blown away by what I'd heard of the story, and the phone overwhelmed me. :P But it was free on GOG, I believe, so I was happy to try it out, at least.

I keep starting the original Last Half of Darkness game and not getting very far with it. It seems a decent enough game (for the time) but I just keep getting drawn away by other things. A shame really because I also have the modern games on hold until I have played those old originals!

For me it's Tex Murphy 1, which I just cannot get into. I got the bundle from gog.

Do I miss out on anything if I skip to the later games?

No. The story is re-told (and better told) in Overseer, anyway.

Martian Memorandum, while very dated in both graphics and gameplay design, is probably worth playing, however. You should probably at least give it a try, and then skip to Under a Killing Moon if you find it's really not your thing.

Paradise is by no means a classic, and certainly doesn't compare with Syberia but I would still recomend giving it another bash and tryign to get past the harem (as long as the poor control systems doesn't drive you completely mad) because that first location is by far the least interesting and atmospheric. The game picks up somewhat after that, in terms of its locations at least. And the cut scenes are gorgeous.

The oldest adventure game by release date that I have but that I haven't completed yet is Colossal Cave Adventure.

The adventure game that I've had the longest that I haven't completed yet is King's Quest VI. I had it on CD when I was little, then I bought it on Steam when the King's Quest pack was on sale. I'm finishing the King's Quest games in order, and I'm on V now, so I should be finally finishing VI soon.