No, Ganondorf's being there was bad, and only hurt the game, as well as Zant, in my opinion. We didn't even know the story had anything to do with Ganondorf until the very end! This made him feel very tacked-on, and I felt that he was there for the sole purpose of making an appearance. That was a bad idea on Nintendo's part, considering that sticking anything into a game only for it to be there is a lousy idea itself. Look at the Slingshot in TP! How did that turn out? Badly done, that's how. It got replaced by the Boomerang, and later the Fairy Bow, way too quickly into the game.
Ganondorf enhanced Zant's personality? Sorry, but I don't see it. Zant was made out to be a very cool, very powerful, usurper until he revealed he followed Ganondorf. Then his character went downhill. He went from a cool, shady character, to a whiny, pathetic brat before you could say "Oh shoot!" Zant revealed that he depended solely on this "god" of his, and then threw a temper-tantrum of a battle. He wasn't even that powerful, as it turns out, since his fight was easy. It was so easy, it was mocking. Of course, this isn't saying much about the game itself, considering all the bosses were total push-overs, Ganondorf included, but I was still majorly disappointed in the fight, as well as Zant's character.
I really think Ganondorf would have fit into the game a lot better, if one of two things were done:
1.) He was said, or implied, from the start to be in the game. Rather than be shocked at his "appearance" later in the game, this way we'd have seen it coming, and would have known that Zant wasn't all he was made out to be. This could have worked for TP, but the next idea would fit in better.
2.) Ganondorf was made out to be the main bad guy from the start. No Zant. At all. Then Nintendo could have given Zant his own game, and made him out to be a much cooler, much more powerful bad guy than he really was in the end. I, personally, think this would have worked, if Nintendo decided to do it. Because, in a way, Ganondorf did belong in TP, but at the same time, due to bad planning and such, he wasn't.
So really, he was a good idea, and he wasn't. In the scenario given in the game itself, he was a bad idea, considering he destroyed Zant's potential, and felt really tacked-on. It was likely just a case of extremely bad planning, lots of ideas floating around, and so on, and it should have been edited and cleaned up at the end, for the end product.