Shin Megami probably has more spin off's then it has main titles, Hell SMT IV is a pretty knew game, and the Spin Off series Persona is already getting it's fifth title at the end of this year. I dont' know if we can really call any of teh SMT games a Spin off at this point.

Having not played pretty much any non US release SMT game, I can say the quality of these titles is easily more consistant then FF on a whole.

Atelier's heights may not reach that of FF or SMT, though they have found a consistant high quality that they rarely fall from, though it is targeted to a smaller audience.

And your lack of mention of Breath of Fire depresses me.