Zuki has a bunch of things going for it. For one thing, it's something new and different. We were all prepared for the comics to be totally uneventful and for nothing important to happen, since of course everything has to lead into Korra and we already know how things turned out there. But Yang then gives us this strange chemistry between Zuko and Suki out of nowhere, when we were least expecting it.
And on top of being unexpected, it's entertaining. They really do have chemistry; Yang manages to give them more warmth and affection for each other in a few panels than Bryke ever achieved with Mai and Zuko throughout the show--and this is despite the fact that there's no overt romance between them. It's enjoyable to see the emotion between them.