"The Longest Journey" is the first game. Its a 2d point and click puzzle adventure game. It is the more highly rated of the two. I have read there are issues (solvable) in running this game on later versions of Windows. There is one puzzle from TLJ that made someone's list of most difficult or convoluted puzzles in the history of gaming.
Nothing beats Gabriel Knight 3's
Cat Mustache puzzle. Oh dear Lord... the gods were angered by this so much that it not only killed the Gabriel Knight franchise for over a decade, but also is called by many to be the sounding gong of the death of adventure games.
Here is the relevant snip:
The infamous “cat hair moustache” puzzle is outlined here. Spoiler Gabriel is staying at a hotel in the small isolated village of Rennes-le-Château, and in order to carry out his necessary investigations, he will need a bike so that he can follow various suspicious people around. There are tour bikes reserved for the use of the tour group, of which Gabriel is not a member. Hence, in order to hire a bike, he must disguise himself as a member of the tour group. That seems reasonable so far... The person Gabriel ends up trying to impersonate is his old pal Mosely, a police officer from New Orleans (an important character from GK1). To achieve this impersonation, Gabriel must obtain some photo ID, a jacket, a hat, and a fake moustache.
Well, there’s nothing illogical about any of that... except for the moustache. Mosely doesn’t even have a moustache. Deducing that Gabriel has to diguise himself as Mosely WITH A MOUSTACHE does not exactly leap out as a likely course of action. In fact, when Gabriel swipes Mosely’s passport (luring his attention by the judicious use of yummy mint candies which Mosely can’t resist), he actually has to draw a fake moustache onto the photograph in it with a black marker pen. The jacket is easily obtained from the coat rack, and the hat is claimed from the Lost Items box at the Museum Saunière. But the moustache...? Ohhh, it’s a tricky one.
Gabriel cannot snip off a few locks of his own hair to create the fake moustache. He cannot find a joke shop or costume shop from which to buy a fake moustache. There is no wig-maker from which he can buy a toupée from which to snip some hair for the makings of a fake moustache. No... none of these are the answer. Instead, Gabriel must observe a cat near the church of St Mary Magdalen, and attempt to pet it. This causes the cat to hotfoot it into a shed via a hole in the shed door.
If only Gabriel could get hold of some cat fur... but all attempts to grab hold of the cat in order to get a bit of its fur will fail. So why not try somehow to obtain some fur in a more roundabout and crazy way? All it takes is some searching of his hotel room (where he finds a piece of masking tape), a look around the hotel dining room (where he takes a sachet of maple syrup from a bowl on the buffet table), and an instructive view of Abbé Arnaud misting his plants with a bottle of spray mister in the cemetery on the grounds of the Church of St Mary Magdalen (where Gabriel waits until the good Abbé has left, and then grabs the spray bottle).
Gabriel now heads back to the shed. He applies some masking tape to the hole through which the cat entered. He sees that the cat is now on a high ledge, and he aims the nozzle of the spray mister at the cat. The cat leaps down and streaks through the hole in the door. Aha! Gabriel takes the masking tape and observes that it has a considerable amount of black cat fur now attached to it. By picking up the masking tape, the fur is transferred automatically into Gabriel’s inventory. Applying the sachet of syrup to the fur makes a sticky moustache. Adding the cap and the sticky moustache to the borrowed jacket completes the making of the disguise, which Gabriel can then wear in order to fool Bigout, the man in charge of hiring out the bikes.
Feast on the nonsense. Relish in its impossibility. All of this... to rent a bike and go to a location up the street.