I did see this in a theater when it was first released, due to an enthusiastic review on Siskel and Ebert.
A site about the _house_ used in the movie did say it was a surprise hit (glad Gene and Roger liked it) and ran
from Thanksgiving till New Year's...
From the book about Shepherd: "Director Bob Clark says that the studio waited too long to reserve venues for its original release in 1983, so at Christmas it was only in about one hundred theaters. (It is said that the movie studio only backed the making of it grudgingly, and did
not promote it much."
However, TV showings and the original video release (and maybe some word of mouth) helped it become a cult classic.
Supposedly some 38.4 million people watched the 2003
TBS A Christmas Story Marathon!