The Legend of Zelda is a franchise that has typically come in two stylistic flavours — top-down 2D/2.5D or fully 3D worlds. The latter began with Ocarina of Time while the former was common on older systems and notably on handhelds, with the DS entries shifting the top-down camera angle slightly. With that in mind NES title Zelda II: The Adventure of Link is an oddity, not just in its naming convention — dropping "The Legend of" — but also in the gameplay it delivered.
With experience points, leveling and a combination of top-down world traversal and side-scrolling action, it's a formula that hasn't been replicated since in the series — unless you want to count the CDi games in some form, which we don't. It's also rather divisive, with some simply not being fans of its style or borderline crippling level of challenge.
This original NES sequel was cited by Miyamoto when asked by Kotaku to name a "bad" game on his CV. The developer explained how the project failed to evolve from early planning, and outlined areas that he would have liked to be better; the first issue is related to load times on the Japan-only Famicom Disk System.
I wouldn't say that I've ever made a bad game, per se, but a game I think we could have done more with was Zelda II: The Adventure of Link.
When we're designing games, we have our plan for what we're going to design but in our process it evolves and grows from there. In Zelda II: The Adventure of Link, unfortunately all we ended up creating was what we had originally planned on paper.
...So one thing, of course, is, from a hardware perspective, if we had been able to have the switch between the scenes speed up, if that had been faster, we could have done more with how we used the sidescrolling vs. the overhead [view] and kind of the interchange between the two. But, because of the limitations on how quickly those scenes changed, we weren't able to.
The other thing, is it would have been nice to have had bigger enemies in the game, but the Famicom/NES hardware wasn't capable of doing that. Certainly, with hardware nowadays you can do that and we have done that, but of course nowadays creating bigger enemies takes a lot of effort.
It's certainly a unique entry in the franchise, and evidently one that was held back by circumstances at the time. What do you think of Zelda II and Shigeru Miyamoto's comments?