The hidden masterpiece of later Queen is Innuendo.
The best song on Hot Space is "Las Palabras de Amor."
"Cool Cat" is, at the very least, more interesting than some of the generic rock crap they stuck on there.
The worst Queen album is The Miracle.
Innuendo is a masterpiece, but with sales of 10 million worldwide I wouldn't say it's hidden. I love The Miracle though it has a few turds on it. Hot Space is truly abysmal, but generic rock isn't why IMO.