The hardest Zelda Ive PLAYED was "A Link to the Past.
That fucking game was difficult.

Zelda II. This isn't an opinion, it's a fact. Anyone that says otherwise is factually wrong. The game is insane.

I don't even know how I managed to beat Shadow Link. There's like no pattern to his vulnerability.

Zelda II no doubt. I am currently playing it again on VC and in the second palace. And it is as hard as I remember...

Zelda II, but partially because that game was bullcrap. Screw Darknuts in that game, man, seriously.

The original game is the hardest that's actually fair.

Master Quest is basically the same thing but the temples/dungeons are altered. It's not really much harder, it's just if you've played Ocarina of Time thoroughly and know the areas really well, it won't help you much. As for a purchase, I'm torn. It is a new experience but essentially the same game. Ah hell, buy it if you want. I'd scope some details of it if I were you.

Zelda II: Adventure of Link..AlttP right after...though much easier

Zelda 2 is basically the hardest overall, but i feel that also because of many elements that make it an entirely different game than all the other Zelda games.
I'm not just talking about the side-scrolling part either; constantly regenerating enemies, no way to recover health in dungeons except ONE single fairy at best and then whatever magic you're willing to sacrifice on it, not being able to avoid enemies, very unclear hints at where to find items, no way to teleport from the starting point to anywhere else so that if you saved and quit you had to trudge through the entire game again, no useful items like bow, boomerang, bottles, hookshot, all of which I think could have made the game far easier if any of them had been present.
I've gotten over my hatred for Zelda 2, it is a good game, hell, an excellent game at what it is, I just still have trouble considering it to spiritually be a real Zelda game due to how many of core elements that I love of the main Zelda series are missing.

With Zelda 2 aside, I'd probably say either Zelda: OoT Master Quest for the 3d series, or if you want to use the top-down list, one/both of the Oracle of Ages/Seasons game(s), I beat one of the oracle games, but I'm still working on the other.

Mater Quest>>>> OoT

better and complex dungeons..and it's great for those who loved OoT, since the dungeons make the game feel new.. XDD

playing through OoT for the 20th time..lol..so familiar..doing Master Quest..LOL: you ACTUALLY have to listen to the deku scrubs again..for once XP

and it's harder than MM..once you understand MM it's easy..but Master Quest to me was harder

At the expense of sounding like a parrot,
Zelda II

Quite frankly the skeleton goons would give me enough trouble since hitting them required exact timing. Never finished that game. For that matter I have never finished the original Zelda (second quest) either. Though it wasn't difficulty it was simply couldn't find some of the temples. And I will never resort to some walkthrough.

Currently I'm playing though the only Zelda that I haven't played which is Windwaker. And it's challenging but no where near as difficult or frustrating as Zelda II

I love the complaints about the knights in Zelda II, that is one of the elements I wish they would translate into the newer Zelda's. They actually required skill and patience to defeat them, they were like mini-puzzles every time you met one, only making it worse by the fact they could continually get better as the game went on, damn blue knights with their throwing swords.

The last boss was hard because you needed to defeat him before your jump spell ran out.

Not to mention all the ghost levels, graveyard and the one with the bridge with randomly appearing ghosts (try to jump a gap and a ghost appears and knocks you into a hole).

Not even mentioning the last dungeon, but the path to the last dungeon is a game in on itself. Starting with with the giant fence moving onto the lava that contained so many narrow paths you had to fight enemies constantly. This even before you managed to make it to the last dungeon.

Anyone even remember the surprising statue knights that would appear and always take away your full health before starting a dungeon.

I must agree with Claude here, anyone that doesn't think Zelda II is the hardest is wrong.