“The murals in restaurants are on a par with the food in museums” is a saying from American novelist Peter De Vries (1910-1993). “I do not know whether the retaliation is intentional or not, but the food in museums is about on a par with the murals in restaurants” is from the De Vries novel No, But I Saw the Movie (1952). “The murals in restaurants are on a par with the food in museums” is from the De Vries novel Madder Music (1977).
 
The food in museums (such as New York’s Metropolitan Museum of Art) has improved and the saying applies less today that it once did.
   
 
Wikipedia: Peter De Vries
Peter De Vries (February 27, 1910 – September 28, 1993) was an American editor and novelist known for his satiric wit. He has been described by the philosopher Daniel Dennett as “probably the funniest writer on religion ever”.
 
Google Books
No, But I Saw the Movie
By Peter De Vries
Boston, MA; Little, Brown
1952
Pg. 225:
“I do not know whether the retaliation is intentional or not, but the food in museums is about on a par with the murals in restaurants.”
   
Google Books
Madder Music
By Peter De Vries
Boston, MA;  Little, Brown and Company
1977
Pg. 92:
“The murals in restaurants are on a par with the food in museums,” Pomfret stated.
 
Google News Archive
14 December 1977, Harlan (KY) Daily Enterprise, “New Books” by Phil Thomas (AP Books Editor), pg. 11, col. 2:
MADDER MUSIC. By Peter De Vries.
(...)
His new wife has a deadbeat brother, an extemporaneous poet named Pomfret, who comes to visit the newlyweds and stays and stays and stays.
 
Pomfret is give into mots—“There are few things more degrading to the human spirit than Brussels sprouts.” “The murals in museums are on a par with the food in museums.”—which delight his sister but drive her husband wild.
   
Google Books
The Portable Curmudgeon
By Jon Winokur
New York, NY: New American Library
1987
Pg. 200:
The murals in restaurants are on a par with the food in museums.
PETER DE VRIES
   
NBCNews.com
Where art tastes great
Appreciate culinary masterpieces at the world’s best museum restaurants
By Farhad Heydari, Forbes Traveler
updated 1/19/2008 5:36:29 PM ET
When the late satirist Peter De Vries launched into a trademark condemnation of the morganatic marriage between art and food, his appraisal seemed downright prophetic. “The murals in restaurants,” the prolific author declared, “are on par with the food in museums.” But while the brilliant analogy might have once been accurate, it no longer rings true for many museums.