The verdict must be, sadly, that Kahn was a major talent who left a pitifully small legacy, due primarily, it seems, to being saddled with inferior material. Her heyday lasted a few short years in the '70s, and it ended with her association with Mel Brooks.
I remember becoming aware of Kahn through Young Frankenstein (I didn't see Blazing Saddles until later), I must have seen her much earlier. I was surprised to learn she was a regular on a short-lived series called Comedy Tonight, which I watched as a kid almost 50 years ago. The cast also included Robert Klein, Peter Boyle and Jerry Lacey, who went on to imitate Bogart in Play It Again, Sam. I remember all of them, and even a couple of the skits they appeared in, but I cannot for the life of me remember any of the female players.
I shall always remember Madeline Kahn as the Bride of Frankenstein, but she also lives on in short videos on You Tube. Madison calls Kahn's performance of Irving Berlin's early ditty "You'd Be Surprised," sung in honor of the composer's 100th birthday, "one of the finest musical performances she ever recorded, a mini-masterpiece of comic timing and lyric poise, grounded in specific characterizations of of gesture and accent."
Of course, Kahn, fearful of being pigeonholed as a comic (as if that were a bad thing), had to be talked into it.
On the other hand, Madison minimizes "Ain't Got No Home" as one of Kahn's "party tricks" (p. 278), but it's how I prefer to remember her:
The guy in the fez reminds me of B. Kliban's Turk.