I feel like the correct answer from me is technically Wizard City, due to the sheer amount of time I've spent there with my various wizards. But to be honest, I've had so many baby wizards quest through there before I decided I didn't like their name (or design, back before the days of the magic mirror) and so they got Abracadabra'd, only to be replaced by new ones who I needed to quest through the world all over again. And after all of that questing, Wizard City looses it's nostalgic gleam for me.
So, I answered Zafaria, as that is the world that I was playing through at the peak of my enjoyment of this game. Coincidentally, it was also around that time that my closest in-game friends were around frequently, which surely has something to do with how much fun I was having with the game at the time. But yeah, when I think about the world I have the most fond memories in, it's Zafaria. Whether this has much to do with Zafaria itself is up for debate, but one way or another, it features heavily in some of my best memories from this game.
I think I was a bit rambly, but oh well...
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