I wasn't sure if I should vote for the best couple who happen to be vampires, or the best vampires that are a couple. The latter would be Angelus and Darla, who are as evil as vampires come, and are even more evil in combination.
But Spike and Dru are the best couple, the most sympatico with each other and accepting of each's foibles. So I voted for both couples.
Louis hated Lestat on some level, and Sookie and Bill constantly broke up. Laszlo and Nadja were cute, but it's been a while since I watched that, and I can't recall their ship much. Edward and Bella were too soppy for words. Don't know the others. Unless you mean the Biblical Adam and Eve? They got thrown out of paradise, but did stay together for about 900 years, so there's that. ๐