Once, because the structure of that album is perfect. There is not a single bad or boring song on that album, and it includes five of the brightest and most beautiful songs Nightwish has ever done. It flies up to the skies and down to earth, crosses sorrow and happiness, and includes soft vocals and dramatic choirs. Plus, it includes my favourite Nightwish song - Ghost Love Score. To me, Nightwish simply can't make a better album than Once is. And if they ever do, they will leave me speechless for at least a week.