Not counting countless indies...

GTA3/Vice City/San Andreas - I just never got into any of them. I really tried to, but they just bored the living hell out of me.

Commandos - Simply got too frustrating for my small brain.

Blood II: The Chosen - I love Blood, and I love Monolith... But... It just sucks. It is boring, repetitive, unpolished, not scary, slow... And the difficulty was really off. I found Normal to have ridiculously hard difficulty spikes, but when switching to Easy, a single pistol shot would insta-gib enemies. I think I ended up playing about 1/3 of it, then uninstalled it and forgot about it.

And coming soon, probably in the next couple of days, after buying it just 3 days ago... Skyrim! - I love Morrowind. I even love Oblivion. I love the new Fallout games. But I am just not liking Skyrim at all.
After I spent hours trying to get past all of the technical problems, tweaking files to make it playable, and installing mods to make the interface slightly more PC-friendly, I finally started to just play the damn thing (with many technical problems still remaining,) and... It's boring. It is boring all around. The characters, the scenery, the story, the towns, the quests, the combat, the skills, the voice work... It just doesn't capture my interest like the other games do. I can't bring myself to care about anything in this world.
I'm really trying to like this. But I just can't. Am I doing something wrong? Can someone who likes it give me some advice on how to make it more interesting?
I can't play it for more than a few minutes without my eyes losing focus, and I start daydreaming and wishing I were playing Call of Duty. (Yes, you read that right.) I'm on the verge of uninstalling.

Random dialogue and quest generator? Are you sure you were playing Morrowind/Oblivion?

Master of Orion III : Oh gods, this one certainly counts.

You don't seem to understand what does random generator means.

Anyway, Morrowind is exactly known for a carefully crafted world and Oblivion is known for... well, it has some great side-quests. The obvious honorable mentions being the one where you enter a painting, thieves questline and dark brotherhood questline.

The original Rayman (although I won it rather than buying, admittedly)
Its like Sonic The Hedgehog without the speed which is like GOG without any games released before 2010 - pointless!

Speaking of Sonic, Sonic Heroes on Xbox dire - horrible camera and too easy to miss coins, I don't understand how they cocked it up so badly after transitioning Sonic into the third dimension so well in the Sonic Adventure games (I also missed the hanging out, free roaming parts between missions from those to)

Quite a few Indies:

Pressure - Looked like a fun vertical racer, like an updated Bumpin' Buggies, turned out to be a vertical shooter dressed up

The Path - looking forward to dark and arty adventure thingy but scoring points for delivering a gothling to a pedo was too much for me!

And probably a load more I may tell you about later when I'm home and have access to all my game lists...

Shank... I could not get used to the controls, and also made me realize that my button mashing days are over. No more Mortal Kombat for me :D

Definitely.

.... its trees.

in the opposite direction, a few games I almost gave up on, but glad I didn't...

Hitman.

The first game in the series has an unforgiving (and I claim broken) stealth mechanic that forces you to play all the missions full on combat style even though 100% of the appeal to me is with the stealth mechanic.

Luckily I forced through and there was at least one game later in the series that had much improved stealth mechanics and gameplay.

LA Noire

The driving mechanics in this game made it completely unplayable. Luckily I stuck with it and they resolved themselves. I'm thinking it was a temp bug of some sort. I almost uninstalled only minutes in. The camera would randomly change directions in the middle of a straight-away. Sometimes I could only see from the tire. Then, I reloaded a save and it didn't do that anymore... Whew!! Additionally, the biggest reason I tried this game was the clue-finding / interrogation... which lacks a lot of logic in places (big pet peeve of mine).

Still... What a neat game. It still has lots of bugs and gameplay issues, but this is one of the more ambitious games I've ever played. With incredible graphics and lip-syncing, each character looks just like the actor doing the voicing... and they have some amazing actors voicing this game. I've even grown to enjoy the driving and have collected 89/95 cars so far. (getting into wrecks is also fun ;) )

GTA III

Far Cry 1

Rainbow Six 1

Is what I am thinking right now.

FTL, Blood II, Diablo 3 and Saint's Row 2.
Are you serious? The game is easy if you know what to do and there are mods that can make it easier.

Morrowind actually has quite bland quests in what you actually do in them (go there, fetch/kill that most of the time), but the storyline is one of the most thought-trough ones I have ever seen.

There are several storylines in the game, including the main quest, and they very nicely interact with each other (EXCEPT for the main quest, sadly. As all quests in it need to be doable, you can't influence it much by other storylines.)

At any rate, I'll just give you a little example: When you're doing quests for Fighter's Guild, at one point, you are given a quest to retrieve a code book from a thieve's guild operative. Now it's a fairly standard fare - you get to that person, kill/rob her (she won't give it voluntarily for understandeable reasons) and bring the book back to the quest giver.

Now that was fairly straightforward, wasn't it? Except not really. If you try to read the codebook, it includes a bunch of seemingly nonsensical words. All Bethseda had to do was to put some nonsense into it and they'd be all good. Except they didn't - the book was ciphered using a fairly common enconding technique, and if you have managed to decode it, you would get a slightly scrambled list of Camonna Tong hideouts which the guild has traded with - Camonna Tong being the local slave-trading operation.

Morrowind is absolutely filled with similar stuff. After you gain some trust in the organisation you are working for, you are going to get a lot of seemingly boring and unimportant quests, but if you actually watch the political situation on the island, everything falls very nicely together and doesn't feel random at all. Some quests of one organization even directly contradict quests of the other, so you are going to hinder something you were trying to achieve by another character.

Yeah, dusting Darth maul with a rocket launcher, i was like 12 then though

Even if I get bored of a game, I usually still leave it on the HDD, just to give it another chance later. I don't recall if I've done exactly that, uninstalled the game completely quite soon after trying it out, and never coming back.

One game has pretty recently come close, but I didn't buy it. Steam had a "play for free" weekend for, I think it was, Left 4 Dead. I found it very dull and repetitive at least as a single-player game, so I uninstalled it long before the free weekend timer was up, and decided not to come back to it, let alone buy it.

EDIT: Oh, was this only about GOG games? I saw some mention e.g. GTA IV.

But do you remember characters other than two or three persons from the main quest? Do you recall some of their unique lines? Their character's traits? Does solving some quest provides character's growth (not you)?

When I was playing it, everyone blurred into one person after a while. Everyone basically uses same words, wanted same things, reacted similarly. It's like with Arx Fatalis. The underground is big, you can learn and do a lot of things. It's rich in activities and sizes of maps, not in characters and world's activity (as for meeting non-aggressive and communicating person in a non-hub map). Or with Gothic.

Hence my former reply.