This exchange between Miyamoto and Iwata comes from the Steel Diver Iwata Asks feature…
Miyamoto: When I was making The Legend of Zelda, it was very plain. (laughs)
Miyamoto: I didn’t think that genre would be seen as something so mainstream. I really didn’t expect the response I got when I first made The Legend of Zelda. A world of swords and magic really wasn’t considered mainstream at the time.
Iwata: Was it? Miyamoto: The Neverending Story almost got really popular around that time. It was a world started off with such a message as: “Here kid, Take this sword.” (laughs) In a word, it was plain.
Iwata: In that sense, The Legend of Zelda and Steel Diver are the same to you.
Miyamoto: I think so. But when I said they’re both plain, I only meant it in the sense that they’re not attention-grabbers. I believe they’re the same in the way that they’re both something fun. It’s just a matter of presentation to get more people interested in it. I think the original themes are relatively plain for most of the games.