Zelda II: The Adventure of Link

The Black Sheep?
The Adventure of Link was the sequel to the highly acclaimed Legend of Zelda, and the second Zelda game ever to be released. (Not counting the Game & Watch Zelda) It is by many considered to be the "black sheep" of the Zelda series, mainly because of its attempt to break away from what would later define the 2D Zelda games, the overhead view. Many saw this as attempt to fix something which wasn't even broken in the first place, and were therefore slightly disappointed with this game. On top of that, its sound track wasn't composed by Koji Kondo and didn't properlly reflect the series, and Link's health was measured in squares as opposed to Hearts.

Pros
The game didn't really feel like a Zelda, but it did have some saving graces. It contributed largely to the overall storyline, introducing such concepts as the Triforce of Courage, characters like Impa and Dark Link, and names like Mido, Rauru and other sages. It also utilised a more RPGish gameplay style with level ups, and a full magic system, though this really didn't improve it at all.