By coming out in English so late it will have to compete with SMTIV, but whether or not it's the best I'm sure it'll be close.
You do realize SMTIV will be out in July, right? That is to say, the English version. Compared to Bravely Default which won't be out until I would guess the tail-end of the year for Europe and early next year for NA.
Yes? The OP asked if we'd consider this the best RPG on the system and by the time many of us can answer we'll have played SMT.