Call of Cthulhu is (of course) Chaosium’s horror role-playing game, based on H. P. Lovecraft’s Cthulhu Mythos. Sandy Petersen’s first edition was published 40 years ago when the field was still young. CoC is very likely Chaosium’s most successful RPG, one of few games of its vintage that has not to my knowledge suffered long periods when it was either out of print or at least hard to find. Quite remarkable, particularly given the usual limited lifespans of licensed products.
I’ve played 2nd and 5th editions (which is to say, the post-Lynn Willis versions). The differences between those editions did not seem so dramatic at the time. 7th on the other hand has somehow become two massive tomes, and a cursory examination indicates some major differences: stats appear to have become much larger, for example, I’m curious how these differences work out in play. Whether that curiosity will overcome my current inability to get through long volumes is a detail to be resolved at a later time.