My favourite one is Portrait of Ruin but I'm, like, the only person in the whole world

(well, me and my brother, by the way).
Yes, Order of Shadows is plain terrible. I'd recommend Mirror of Fate first, against OoS, but none of them are MetroidVania in my opinion.
It could also be said that Harmony of Despair is MetroidVania... kind of, sort of...
To be honest, Metroid games can't be MetroidVanias. They are just Metroid, yes. But they are definitely not Vanias.