While technically, they'd be referred to as dead ends, in my mind, if there is stuff that you forget to pick up, and then just a couple short screens later you are stuck in a position where you can't return to get that stuff, but you need it for a puzzle in front of you, I wouldn't REALLY consider that one of those game-breaking dead-ends, since you can probably reload a save you had (stuff like what Blueskirt mentioned about KQ5 near the end in Mordack's castle). The explanation I agree to is when it is described as "forget to do or do something wrong at the beginning of the game, and then near the end of the game (or much later, I guess), you get stuck (or even killed)".
Again, while today I have no patience for that sort of gameplay, back when these games came out, I understood that these games operated with a certain ruleset of what was expected of the player, and what was expected of the game. Many of these don't make "realistic" sense , but there they were:
You were expected to have multiple saves, and constantly create new ones (you were probably expected to save before attempting any "new" thing).
You were expected not to do anything obviously stupid (or at least save before doing it, doing it, watching the result, then reloading)
You were expected to try and pick up everything.
You were expected to explore as much as possible, but still always save first.
There were a couple of times when Sierra itself turned these rules on its head, of course, which I found annoying and unfair. The unstable ordinance in SQ4 was an example. The boulder rolling over and killing you if were on the wrong side in KQ1 (which I care about less, because I don't really consider it a relevant game in terms of puzzle design or immersion in the game world, it was just the first at what it did) is another example. Mazes generally operated on a completely different ruleset from the rest of the game as well (take out some paper and plot the maze, save every screen, save before going to the next screen, you are very probably EXPECTED to have to die several times to do this properly, etc.), but again, it was generally understood that this is the way it was.
As far as the original topic is concerned, if it is still relevant in any way, I'd recommend:
King's Quest 5 (with the caveat that you should understand that you should pick up everything you find, and if there is a cat doing bad things, THROW SOMETHING AT IT , and be careful what you eat, and don't eat too much ) and 6
SQ1 (I personally prefer the VGA remake), 3 and 4 (and 5 if you REALLY want to)..
Quest for Glory 1, 2 (you might like the VGA remake AGDI did for that, I haven't really played it fully, though), and 4.
I'd definitely recommend Gabriel Knight 1. I wasn't too fond of the FMV of 2, and I don't share Ali's love of 3, but sure, you can check those out if you feel like it.
I'd also recommend Conquest of Longbow, and if you are able to overcome the more slightly troublesome interface (and slightly more evil puzzle design ), I'd definitely recommend Conquest of Camelot and The Colonel's Bequest.
You might also want to try Heart of China from the Dynamix Games Sierra published. I'd recommend Willy Beamish too, but I'm not sure if that is just my nostalgia speaking...it was difficult in such an insanely scary, yet hilarious way. Snake will back me up on that . I've heard Rise of the Dragon is also great.
Perhaps it is my personal taste, but I could never really care for the Police Quests (they just seemed to be "follow police procedure to the dot, and win"), Leisure Suit Larrys, and Freddy Pharkas (the aimlessness and lack of goals of the first half of the game didn't motivate me enough to continue, even though it seemed very well made otherwise).
If I had to choose much fewer, I'd say KQ6, SQ4 (and maybe 3), QfG4, GK1
* Babar embarrasedly confesses to have not realised Technocrat was only talking about KQ.
So yeah...play KQ6.
PS: Ilyich, if you didn't like ANYTHING about Monkey Island 2 (the music, the atmosphere, the humour), then yes, something is wrong with you