Well, I remember that era, the Commodore, Spectrum, CPC, Amiga, etc.
Japanese games were wrongly considered as easier games.
They were easier, but because three reasons:
1.- They were much more user friendly. Less keys. Crearer controls. Cleaner interface. Menus of one or as much two deep levels. Less painfully consequences to the errors. You only need to compare Dragon Quest I with the Ultima I or Wizardry games that they use as reference, and Dragon Quest seemed a educative RPG, in that era.
2.- They balanced the difficulty. Japanese games were hard, but at least they were possible to finish. Western developers made games that only 1% of the people who played them was able to finish. Energy based games were very few in the occidental market, nearly all the occidental platform games of 80's was life based games with blocky collisions where you got killed if you got too close to the enemy. With dirty one-fail-game-over tricks, when failing to certain pits will imply that all your remaining lives will be lost respawning and falling to the same pit.
3.- They used game designers. In western games, in 80's, there weren't game designers, the programmer was also the designer and, sometimes, even the artist. That's why a lot of old western game designers (Sim Meier, Molyneux, etc) started as programmers, but also, if the programmer was too closed-minded, the game was a selfish sadistic challenge of the programmers to the players.
I still love some of those stupid impossible games, and when I was a child I preferred them over the japanese simpler and easier games. But obviously, japanese games were better, even if we didn't know it.
For example, Mission Elevator: It was a kind of rippoff of Elevator Action. And it was uber-complex. You need to look in the different furnitures looking for clues about where it was the key (pressing down), but sometimes that makes you kill because of crouching to avoid a bullet when you were next to an electric outlet. You got money from furnitures, and you need to look in the doors for guy that will give you the key to the next zone (but that guy only appear if you already found a certain object in the furnitures). Also, you was going up, instead of down.
The game was great. But it was not so straigh-forward as the game that tried to copy. It was really difficult and very slow-paced.