Ingrid, perhaps even more than Grete, doesn't seem to get enough credit for her achievements these days. For some years between about 1984 and 1990, she was the dominant female distance runner in the world, putting up times that compare very well to times in much more closely competed (and orchestrated) races.
I'm a little hesitant to call Ingrid "superior" to Grete, at least as to the complete corpus of her accomplishments in running. Perhaps if Ingrid had focused less on cross-country skiing and more on running in her early years, she would have had a similarly lengthy resume of world-class running, but she didn't really start hitting her stride until about 1984 (in the London marathon, I believe), and her apparent dominance during the next five or six years was punctuated by three major failures -- (1) her fourth-place finish (not just behind Joanie and Grete, but also behind Rosa Mota) in the 1984 Olympic marathon, (2) her loss against Joanie in their riveting battle at the 1985 Chicago marathon, and (3) her very unfortunate injury leading up to (and including) the 1988 Olympic Games, where a gold medal would have seemed an almost foregone conclusion. But yes, when she was on, she was the best female runner at quite a range of distances, fully deserving of a place among the all-time greats of women's distance running.