Gradius
There are plenty of other changes that had to be made to accommodate for memory limitations of a cartridge in 1986 though.
NES
Hokuto no Ken
Of course all of the game’s mechanics were detailed in the manual, but if you don’t have it (or access to the Internet, if you’re playing this in modern times) then you will probably never make it past the first stage.
Dragon Ball: Daimaou Fukkatsu
Akira Toriyama himself actually played this game with his wife over the course of two days. He commented in an issue of Weekly Shounen Jump that “It was pretty rough dying immediately from a game over, but it was faithful to my source material and I was very excited about the differences. They weren’t all that far removed from it, and I really liked Konpei”.
Gegege no Kitarou: Youkai Daimakyou
And though the game tells no story on its own, fans of Gegege no Kitarou will find plenty to appreciate in the details.
Ys
…the Famicom port is not considered to be of very high quality when compared to all of the other Ys ports.