I was hugely impressed with the Cleveland Museum of Art when I visited last month. A really vast collection. It takes several days. I also finally visited the Barnes, which we found absolutely exquisite. The Virginia Museum of Fine Arts is also impressive, especially the Paul Mellon collection. I really enjoyed the English hunting and equestrian painting s from the 18th century.
I walk through museums all over the world. One of the most interesting is the WW2 museum in Gdańsk. Massive and expertly curated in a post-modern building.
As for the Prado, I agree that it’s superior to the Louvre. I went in at opening and forced myself to just wander through the galleries without a plan. It was worth it.