Kaname x Yuuki.
I believe kuro_neko003 explained it very nicely as to why KanaYuki is much better than Zeki. While it may be true that Zero needs her more (because he is too emo that he has to be dependant on someone else like Yuuki), I think Kaname's past is way more tragic than Zero. Unlike Zero, Kaname tends to keep his pain to himself, because he doesn't like to put the burden on the other people's shoulder. We don't know what lingers within his lonely eyes. I find his character more appealing. Beside, I never liked Zero. I don't understand how Zero and Yuuki's relationship could work out seeing as they have incestual relationship *no offence* (step brother and sister), and its totally out of the vampire plot. Nothing would be achieved by having Zeki ending. The theme itself is about the co-existance between vampires and humans. If you think about it, only Kaname and Yuuki relationship fits with the theme. Just because Zero and Yuuki spent more times together than KanaYuki doesn't necessarily mean they will end up together in the end. Time doesn't measure the length of love. Kaname always stands up for his love. He can be the villan of the story, but that dosen't matter to me, because the only thing that matters is his love for Yuuki. And I loved chapter 30
Spoiler (highlight to view)
(Kaname's confession)
. I think the author is trying to build up an ultimate relationship between Kaname and Yuuki. They ain't gonna be isolated from each other because they are too different. I've always been positive about KanaYuki ending. But there are times when I wanted Yuuki get ouf of the way, because Kaname is simply too good for her.