I agree that Jorma and Jack are both EXTREMELY underrated, especially Jack.
I think a lot of this has to do with two things:
We live in a bit of a self indulgent generation, where bands like Led Zeppelin and such rule as KING of the "true" music lover. While they're meritorious in their own right, I think bands like the Airplane, Dead, Who, etc. were a little more sincere. However, they didn't have a gimmick, and are sorta lost to the annals of history. For instance, no disrespect to the Doors, they're great, but Jim Morrison was still more of an actor than a singer, more drama than music. And which name do you think comes up more - his or Marty Balin's? Kantner? Slick?
Second point - I think Jorma and Jack are kinda unjustly forgotten (along with Spencer, by the way) because they were the instrumental axis of the Airplane, which were, at least by comparison to say, the Dead (who were great but never really had any distinctive singing) a VERY vocally oriented band. They had not one, not two, but THREE singers (two of whom were REALLY impressive - sorry, Paul, nothin' personal), all three also capable of extremely unique songwriting. This tends to kinda overshadow the people PLAYING those compositions.
Anyway, sorry to ramble, just my thoughts. And all hail Jorma and Jack (and Spencer, may he rest in peace).
"War's good business, so give your sons
But I'd rather have my country die for me" ~ Grace Slick, Rejoyce 1967