As for ALNICO - even if there are "better" (read: stronger, smaller (=concentrated) and more homogenous field emitting) magnets on hand today, the "oldschool" Alnico as well as the rare earth samarium-cobalts magnets in cartridges old and new often (not always....) do have a sense of "rightness" and "live-likeness" going with them. I suppose however that this is a kind of side-effect of and interaction with human hearing similar to the 2nd order harmonic distortion which is one of the technical basis of the seductive sound some SET-amplifiers can produce in the ears and minds of some many listeners.
On the large scale however I think one single parameter is paramount in the design of a true outstanding cartridge.
The clear concept in the mind of its designer and (most important..) his individual taste in sound and the ability to bring this particular taste into sonic output.
Isamu Ikeda and Takeda certainly didn't design outstanding cartridges because they are technically better in this than other skilled designers.
Or because they used mysterious materials others didn't find out about.
Maybe they just had a very attractive and precise vision about the sound they wanted.
And didn't settle for less than a product which did exactly what they had in mind.