Well, I have to agree pretty much with the majority here:
Puzzle-wise, SS is the easiest Zelda I've played to date (and I've played them all except the Game&Watch, CDi, FS and DS games) and that holds true for both main quest only and 100%ing it*
That's because the game is very linear (most linear Zelda game to date IMO) and the puzzles are all self-explanatory. However, I still had my fun solving them and while I think they should have hidden some solutions a bit more, made the game less linear and Fi's interrupting scenes optional (like when you first meet the Lizalfos), I'm glad that you didn't have to burn every bush and bomb every wall to advance a small step like in the original LoZ, this way the game would've probably taken me 1000 hours to complete...
Combat-wise however, I think it's the hardest since AoL (MM might be an exception in some cases), even though that doesn't mean much because all of the Zelda games since aLttP were relatively easy in that aspect. (Not that this is a bad thing, I'd rather have a physically "easy" game that is beatable without game overs if you use your brain a little than an insanely difficult and at parts frustratingly hard game like Shadow of the Colossus, in which I never made it past the first boss or AoL where Death Mountain is to be taken literally)
Let's look into them:
- aLttP, I can beat it without problems 100% in 4 hours and no game overs (might be my almost 20 years of experience with that game which is BTW my favourite Zelda along with MM, but still one has to admit that it's rather easy). Bosses are all easy to figure out, the only things that give me occasional trouble are the Blind and Mothula battles (that's why I usually get my lvl 4 sword before going to Mothula, yay for non-linearity!), Ganon's Tower and the final battle against him, but they are all manageable with some fairies/potions and in my opinion that's how it should be like.
- OoT is even easier, even on my three heart run I died only once when I was going through the Haunted Wasteland with 2 hearts and a leever hit me (-1 heart) and by doing so that f***er pushed me off the track (another -1 heart and no fairies at that moment = game over). The final Ganon battle is actually easier than Ganondorf, all you have to do is roll under his legs and slash, you don't even need an ounce of magic to defeat him, just watch his very slow attack pattern and use your chances. I'm always using the Biggoron's Sword in the first phase though but I'm sure it also works with the hammer. Oh, and Ironknuckles who are supposed to be the hardest enemy in the game are so easy to figure out, all it tackes is the backflip/slash method. Now, if we had to face three or more at once, then THAT would've been a nice challenge!
- MM isn't that hard combat-wise either but definitely above OoT. Especially Gyorg and Igos du Ikana always nearly kill me, but the final battle can be beaten with 3 hearts and without FDM problemlessly (Château de Romani is highly recommended though)
- WW was the absolute joke when it came to combat difficulty, I never went below 3/4 of my health except in the very final battle.
- TP wasn't all that easy as WW but still not much above it. At least falling in the lava cost you 2 hearts this time around. But all the bosses were blatantly easy to figure out, just the beast form of Ganon gave me some trouble because I had a hard time lining up and timing the attack perfectly with the wolf but even that cost me 5 hearts max. The darknuts were fun to battle though, finally an enemy in a 3D Zelda that involved some strategy.
Now while I can beat all of these games without game overs easily, I had 3 in my first normal mode playthrough of SS and easily over 10 in Hero Mode until now (but all of them were in the first third of the game, once you get the heart medal things become a lot easier). Enemies finally do more damage again, comparable to the original LoZ and sometimes it's hard for me to see when a boss is just charging up for an attack so I can defend by either blocking or evading in time, especially Ghirahim III.
*By 100%ing, I don't mean collecting 99 of every insect and treasure, and not even having the full 9900 rupees, because that's just totally pointless. I mean really, collecting 99 Goddess Plumes - isn't that impossible at all because they're only found in chests and some fixed locations once? Or can you buy them from that Sheikah stone for 200 rupees each? If so then it's still quite a useless chore to grind up 20K rupees just for that. And that's only one of 16 treasures... I mean the golden skulls are (my guess) a 1:100 drop from Bokoblins, do you really want to kill ~10,000 bokoblins for that? Or those claws which I think are a 1:50 drop from keese. Or catching 99 blue feathers. Or 99 units of tumbleweed (I always was low on that). Nah, in my book 100% just means finishing every sidequest (including all gratitude crystals and goddess cubes), getting all the heart pieces, the best shield (Hylian) and all upgrades for every item at least once (beetle, shields, bow, arrow/seed/bomb bags etc.), not even setting the world record for the bamboo cutting game (what will it be, 50?) or a perfect minesweeper game, because chances for getting that perfect are, roughly estimated, in the 1:1 million ~ 1:1 billion range.