Some of the picks on that list are... choiceful. However, I can understand the rationale behind Always Be My Baby being the ultimate Mariah song. It combines all of her best instincts, eras and sensibilities into an enduring bop.
I will say that MC30 has caused me to re-evaluate her catalogue in a way that I haven't done for years. I have come round to Charmbracelet. I have re-discovered the organic 70s soul back-end of Emancipation. I genuinely, finally and truly understand why, in December 1999, I declared Rainbow the greatest album ever recorded (it slaps). I have even more love for Emotions than ever. However, Butterfly remains her magnum opus - every song is a 16/10.