The events of his childhood and early life lead to his attack on Hyrule, which leads to fighting Link in OoT. Every appearance after this is the same person either in the same life like in TP or having just been freed from a seal or resurrected.
It wasn't just setting up for Ganondorf. Demise's curse is that Link and Zelda's descendants will constantly be challenged by a great evil, with that evil essentially being a reincarnation of Demise's hatred.
In that sense, Ganondorf, Vaati, Majora(probably), Malladus etc. are all part of the curse. Demise's story in SS does do at least one important thing, and that is that it explains why there is always a Link and (almost) always a Zelda.
I'm pretty sure the only Ganon that's different is the Four Swords Ganon. The LttP/LBW/LoZ Ganon's are all being continuously resurrected after being sealed or w/e, he only really dies in WW and TP.
There are at least three different Ganons, I'd have to take a look at Hyrule Historia again to see if there are more, but at least the three main branches all have separate Ganons.
And as Aurath8 mentioned, it's not necessarily Ganon that embodies the curse every time.
Throwing the rest of the villains in like that is ok because they don't have the same type of backstory, although for Majora it really seems like a push.
I just looked back at Hyrule Historia, they are all the same Ganon, just in separate universes (due to the branches introduced at the end of OoT). And even at the end of Wind Waker Ganondorf isn't killed, merely turned to stone. I don't remember what happens to him at the end of Twilight Princess though.
That it also serves as a passable explanation for why WW Link had to jump through so many hoops to become a Hero helps, too.
"Hey! Don't pawn your trash on me!" Watchy Watchog
...And also welcome to the "chosen hero" trope which is in basically every Zelda game ever made, and is in fact, not exclusive to Skyward Sword at all.
...That being said, Skyward Sword was even more Zelda-like than most of the recent entries in the series, and I mean that in the worst sense. Sorry, but that's the impression I got.
Last edited by Aegiscalibur; 6th April 2015 at 2:52 PM.