Nintendo's follow up to the smash hit Zelda detracts a lot from the formula of the first game. This game seems to be the black sheep of the family, with good reason.
The biggest difference you see here is that the "action" portions of the game have been switched to a side scrolling, hack n' slash style. The main overworld however is done in a more traditional RPG style, with an icon representing link that switches to the side scrolling portions when encountering a monster (a system similar to Gargoyle's Quest, although this game came first.) While this convention works for the most part it suffers from the same problem that all other games that use it do: Enemy encounters seem to occur completely at random, and at times can become a pain in the bootay. You are able to see the monsters coming (unlike other RPGs from this time,) however most of the time they move too fast for you to effectively dodge. There are some areas in the game toward the end where literally every single step you take is interrupted by monsters, making the simple act of walking down the corridor a chore. Detracts from the fun somewhat.
There are other major differences here as well. This game uses an experience point and magic point system unlike all the other Zeldas. Once you level up (which usually happens upon completing a dungeon) you get to decide on which stat you want to increase, health, attack, magic, etc. You also get experience points from normal little enemies along the way, but as per usual in games of this type it takes a god awful amount of time to actually get anywhere by killing the weaker monsters.
Combat is realized in a side scrolling fashion, similar to other action/platforming games at the time. These action sequences play out rather well. Link is able to (eventually) bust out with several different sword strokes, including an upward and downward thrust, and by the end of the game with higher stats becomes pretty much unstoppable to everything except the major boss characters. Unlike in all the other Zelda games you don't get any secondary weapons: no boomerangs, bows and arrows, etc. Instead you get magic spells that do various things, increase jumping height, defense, shoot fireballs, or turn all of the enemies on the screen into weaker "bots." As with the attack and life stats, the effectiveness of your magic increases as the magic stat increases.
Good stuff: The game is pretty large, with lots of areas to check out. There are seven different palaces (dungeons) that are laid out decently, with lots of elevators, hidden rooms, etc. Side scrolling combat works pretty well, with lots of different enemy types that all have their own unique attack patterns and weaknesses. There are also lots of little side quests to undertake in the various towns and such that need to be completed in order to obtain all of the various treasures. The boss characters are pretty imaginative for this time and overall the game has a good difficulty curve.
Bad stuff: The overworld can get pretty monotonous and confusing. It's easy to forget exactly where you are as all the icons for the terrain, palaces, and towns tend to look the same. The monster encounters tend to happen a little too much toward the end of the game, and in the beginning until you get the thrust moves and some decent stats you're better off just running away when possible. The lack of secondary weapons and reliance on spells means you spend a lot of time seeking out magic potions and dodging low swooping bats and such when a well placed boomerang solves the problem in all the other Zelda games.
Overall: Most fans of the later (excellent) Zelda games on the N64, SNES, and other systems probably won't like this chapter in the story as it detracts too much from the winning formula. The game has a lot more in common with other side scrolling RPGs that came out around the same time like Castlevania II or Battle of Olympus, both of which are good games. But they're not Zelda.
Graphics: Overworld map is somewhat bland, with blocky terrain graphics and vauge icons. The side scrolling graphics look a lot better however. Link looks good and animates well. The rest of the characters in the game aren't looking so good, most of them use a small color palate (two or three colors each) and have simple animations. One gets the feeling graphics were sacrificed somewhat due to the size of the game.
Sound: Catchy music abounds. Some of the overworld music can get pretty annoying at times. In game effects are well done.
Gameplay: The action sequences generally shine while in the palaces and other unique places (bridges, caves, etc.) Random encounters in the overworld get a bit old after a while, but except for a few areas this isn't too annoying. The step-n-fetchit quests seem outdated to us today but were par for the course at the time. Overall it does a good job of keeping you interested until the end for the most part.