Great material? Come on!! How about most of the entire album "Surrealistic Pillow" and of course, "After Bathing at Baxter's". The interplay between Jorma and Cassady is some of the best and most innovative in rock history. They took blues riffs, splattered some acid all over it, and voila...
"Built this City" doesn't count in my book. It's the third generation of Starship with Mickey Thomas running the plane. No, listen to the era 1965-70 and there is undeniably great writing, singing, and playing.
I saw Kantner's Jefferson Starship (not to be confused with Mickey Thomas's Starship, which he still hauls around) at the Chet Helms Memorial Stomp last year and they were great. Kantner was the only true original as Balin skipped that gig (how could he miss a memorial for the Family Dog??) but he had David Freiberg of the Jeff Starship (and formerly of Quicksilver) and Slick Aquilar on guitar who is quite good. The "new Grace Slick" is a wonderful singer, I think it Diana Mangano. Kantner is a crackup, playing hippie rock star still -- chain-smoking, and holding court. He still rocks too.