I thought this would be a really easy list to write, but when I thought about it, I couldn't describe what is so amazing about Zutara. This doesn't give the ship justice, but I tried. If I can think of better reasons, I'll post them.
12. It's a whole lot more interesting than Kataang or Maiko.
11. The hints ARE there.
10. They need each other.
9. They're gone through so much, together and alone.
8. It's far more complicated and passionate than Kataang.
7. Sometimes it's fun to be hated. Oh, AvatarSpirit/Bryke/everyone... why do you hate Zutarians so?
6. Zutara defies all odds.
5. It's inspiring, it's exciting, it's intriguing, sparks fly.
4. It shows that love can transcend the boundaries of nation/race and good vs. evil.
3. They need each other. They are both deep people, and while I'm not saying Aang isn't, I honestly don't think he understand Katara the way Zuko can. I recognize that he has lost people, too, that he has lost everything, but I feel like Zuko is far more similar to Katara.
2. I find it more interesting to have faith in a ship even if it's not always obvious.
1. There's something pretty amazing about the fact that less than 10 episodes after Katara, in all seriousness, threatens to kill Zuko if he makes on wrong move, he takes lightning for her.