CURSE OF FRANKENSTEIN was really the first (barring the SF stuff such as the Quatermass series). When Hammer went ahead with DRACULA, intially Universal picked it up and it wasn't until the rights reverted back that WB/Seven Arts picked it up. Ditto on THE MUMMY.

Generally, it was my thought that the trend changed in general with society. Old-fashioned Grand Guignol went out for the modern horrors that were prevalent with the scientific age of the '50s. What was in outer space was far more relevant than what was going on in Transylvannia.