Zelda's first sequel (Link, in the late 1987) was radically different from the first and, at the time, not very well received. It was a good game in its own right, but very different from the original Zelda (with an experience-points system, a magic system, and most notably, all combat in side-scrolling levels) so a lot of people were disappointed by it.
This was "the lesson" with regard to sequels that differ too much from the original game. People (in the aggregate) want expansion of something they already like, not radical revision.
Examples of successful sequeling would be the Dragon Warrior series. Dragon Warrior II (the worst of the series; enemies tended to gang up on one character and that made it nearly unplayable, esp. with the princess being ungodly weak and dying constantly) is an example of that. It was an expansion on top of Dragon Warrior I, and that expansion was roughly implemented and painful, but the core game concepts of DW 1 remained and it paved the way for DW 3 and 4 (which were among the best NES games) to be made.
This was "the lesson" with regard to sequels that differ too much from the original game. People (in the aggregate) want expansion of something they already like, not radical revision.
Examples of successful sequeling would be the Dragon Warrior series. Dragon Warrior II (the worst of the series; enemies tended to gang up on one character and that made it nearly unplayable, esp. with the princess being ungodly weak and dying constantly) is an example of that. It was an expansion on top of Dragon Warrior I, and that expansion was roughly implemented and painful, but the core game concepts of DW 1 remained and it paved the way for DW 3 and 4 (which were among the best NES games) to be made.