A lover of more intimate buildings, they might have called these the grandest, rather than most beautiful, as I see it. In the eye of the beholder and all that implies. A smaller building seems to tell me more, though, about the subjects on display and the origins of the building and collection. For instance, I much prefer the old Getty in Malibu to the new one shown in the link, more building than content by far, monument to ego.
In any case, here are some I find more "beautiful."
www.musee-jacquemart-andre.com
http://www.musee-delacroix.fr/fr/
http://www.nationaltrust.org.uk/575-wandsworth-road/
Possibly my all-time favorite, Leighton House in London:
https://www.rbkc.gov.uk/subsit...m/aboutthehouse.aspx