There is limited shot data available prior to NHL officially began tracking shots in the 1980s, but shot data has been compiled for the period for 1955-1967. I thought to take a look at that period, which covers most of the careers of three of the general consensus best goalies ever (Hall, Plante, Sawchuk), and calculate expected shutout numbers for those three goalies, as well as contemporaries Johnny Bower and Gump Worsley.
Glenn Hall: 67 SO, 42.9 Exp SO, +24.1, +56%
Terry Sawchuk: 55 SO, 38.6 Exp SO, +16.4, +42%
Jacques Plante: 58 SO, 42.1 Exp SO, +15.9, +38%
Johnny Bower: 26 SO, 19.6 Exp SO, +6.4, +33%
Gump Worsley: 27 SO, 25.5 Exp SO, +1.5, +6%
I am a bit suprised that Sawchuk beats out Plante, especially since this sample includes nearly all of Plante's Montreal career but does not include Sawchuk's seasons from 1950-54 in Detroit where Sawchuk put up 45 shutouts. However, it is very close between the two of them and Bower for second place behind Hall, and the numbers show why all four of them are considered all-time greats.