I love Battle of Olympus! But I haven't played it in many, many years. I keep hoping that it will resurface for Virtual Console or something similar.
I'll second that notion. I always thought there were similarities between the two as well. I was checking out a
youtube video on Battle of Olympus, and you can see some obvious similarities between the two games, particularly in the hero's character design and the backgrounds inside the houses. I think Battle of Olympus was released a little over a year later than Zelda 2 in Japan, and it has aged much, much better. The game, overall looks more visually interesting than Zelda; that year made a big difference.
I say this because I started my playthrough of Zelda 2 last night. One thing that struck me: the game's backgrounds and color pallete are far more bland and Spartan than I remember. I'm far more fond of some of the enemy character sprites, though. I still think the Goriyas, Stalfos, Ironknuckles (Darknuts), Lizardmen, Bird Knights, etc. look very, very cool. As a kid, I was so taken with the whole Zelda mythos, that I loved seeing these guys return in this game.
Also, the text seems painfully primative, and the translation is horrible. For instance, one of the early clues in the first town, Rauru, is misleading. I believe one of the NPCs say something like, "Get candle in Parapa Palace. Go West." Well, Parapa palace (and the candle) are both in the east, which leads me to believe that the intended meaning was to go west
after you get the candle. As a young kid, I wasted a lot of time at the beginning of this game as a kid trying to find where I should go.
Anyway, that interview with Miyamoto is very interesting. It sounds as if they took one of Miyamoto's original concepts, but that he didn't really have that much say in the final product. Perhaps at that point in his career, he didn't have the autonomy over projects that he appears to have now.
Still, even if Zelda 2 was "sort of a failure", there are elements from that game that were used in many of the later Zeldas. The game introduced the Triforce of Courage. The names of the towns that were used as the names of the Sages in OoT (with the exception of Impa), one town was also named Mido (the character in Kokori forest in OoT). The reflective shield (only implemented as a spell here) was used later on as the mirror shield in various sequels.
Last but not least, this is the first use of Link's shadow as a boss character. I was actually disappointed that Link's Shadow was the FINAL boss in Zelda 2, especially after they teased the return of Ganon in the manual and the game. I suppose that this made more narrative sense since this was more of a personal quest for Link, and he had to face his "dark side" in order to obtain the Triforce of Courage. There are probably others, but I can't think of them right now.