I wouldn't have put Ruddigore in their top 3 famous plays. I could easily see someone calling Coriolanus "obscure" without meaning any diss to Shakespeare's popularity.

I guess I know a disproportionate percentage of people for whom it's top-shelf G&S. Now I'm even more tempted. Karr's just got such a visible thing for it as a canon—if the bibliography on her now-deceased website is accurate, her first publication was a Murgatroyd coat of arms in a 1970 issue of The Savoyard. Not to mention a couple of related-looking articles. And then all the crossovers.