By “favorite fictional character” I don’t mean “favorite character of your favorite fiction”, consider the media itself to be irrelevant.
Just consider the character itself and how it changes throughout whichever segments of its timeline, regardless of how the world moves around it (unless it’s relevant);
the show / book / comic / game / political campaign itself may be absolute trash, but you love some character from that more than any other character from anything at all.
Like Magnifico from Wish, or the driver from Big Rigs: Over the Road Racing.
Considering how much time was spent on Zuko I always felt that Sokka was the stronger character
I don’t know about Zuko being less strong, he did betray his father (and temporarily abandon his girlfriend) just to follow his moral compass; his runtime (and his first faux-turnaround at the end of book 2) highlight how difficult it was for him.
Sokka only had do smarten and humble himself a bit, which is no easy feat either, but easier by comparison.
… which is why if I had to pick a favorite from A:TLA, I’d choose Iroh.
Zuko was never really evil, but, where he took his time to look at his moral compass, Iroh had to experience geomagnetic reversal and made it out alive.
WITHOUT a kind uncle nudging him in the right direction.