In my honest opinion? Let me first say that I've never finished playing OoT and I only played the HD remaster of WW on Wii U, which I didn't finish either. (Both games are very good, I just couldn't get myself to finish them.) Skyward Sword is the second Zelda game that I've ever finished 100% from beginning to end (the first was ALttP).
The sky world isn't huge. You start out on a small "island" (Skyloft) that has only a handful of POI (points of interest) that you keep going back to during the game. Then there are dozens of scattered "mini-islands" that you can fly to usually to look for treasure. Just the flying alone is tedious though and there's very little to do in this part of the game. I'm not going to spoil it for you, but the most "exciting" part about this part is delivering pumpkin soup from one location to another within a time limit. That's the most exciting part. (Light sarcasm here.)
Then there's the world on the ground, which is split into a few areas, which are then split into (usually) two areas so you come back to a particular place after acquiring an item that allows you to go deeper into the forest, etc. The problem here is that these areas feel very isolated and while some of them are fairly big, there's really not much in terms of exploration here. It's a small overworld. Finally there are the dungeons, which unfortunately are very formulaic and once you get the hang of one dungeon it's very easy to progress in the later ones because you get enough cues to guess the correct path with little trial and error. There are some puzzles in this game, but I can't really call searching for a key or forming a pattern in a dungeon to proceed to the next room a "puzzle".
Perhaps the hardest dungeon has you carrying a "sphere" (I don't remember what it's called anymore) that activates electric devices around it and you walk around an ancient place where robots, mechanisms, and other stuff come to life when you get to them with the sphere. But even that is all about carrying that sphere with you, throwing it into certain places to activate some triggers, go pick it up again, rinse and repeat. It was a difficult dungeon only because you couldn't defend yourself while carrying the sphere so you'd have to put it down and slay some enemies before proceeding. Which is to say, the hardest dungeon in the game is more frustrating than it is actually challenging.
Boss fights are very predictable and easy. I was surprised on my first playthrough that I actually beat Demise (the final boss) without using the "skyward sword" strike. I didn't even think of it and just kept blocking his attacks, hopping to the sides, and slashing. Rinse and repeat. Every guide I've read recommends using the skyward strike, which is the most powerful attack you can perform, but I didn't even think of it and still beat the final boss. That alone probably says something about the difficulty level. I played again in Hero mode and it doesn't get any better, you just strike enemies a few more times before they drop dead. That's it.
Sorry for the long post. I tried to be as detailed as I could from my experiences with the game (and without spoiling too much I hope). I could sum it all up saying SS was mundane. I played it only because it tells the origin story of the Legend of Zelda. For any other reason I wouldn't play it again, though. In contrast, I've made it a habit to play ALttP from beginning to end every June exactly a week after my birthday because that's how long it took me to originally complete the game as a kid when I got it for my birthday.
That's a game I keep enjoying going back to and finding new unique things to it on every playthrough. I never felt that way with SS despite playing it through twice, first on Normal and then on Hero mode.
