"Stormbringer is a fantasy role-playing game that is part of the Basic Role Playing System by Chaosium. The game places characters in the world of the Young Kingdoms, based on the Elric of Melniboné books by Michael Moorcock.
states that the 1st through 3rd editions are functionally similar with the magic system extensively changed with the 4th edition. Other websites essentially confirm this information. The artwork for the first and second editions is essentially the same. This usually indicates that the rules weren't changed much at all. Another difference between the 1st and 2nd editions is that the 1st edition rulebook was divided into three books and the second edition box was narrower.
The third edition was a hardcover book produced by Games Workshop and also contained the "Stormbringer Companion".
The 2nd edition also featured a 1987 French edition published by Oriflam and 1988 Japanese edition published by Hobby Japan with cover art by Yoshitaka Amano. The 3rd edition featured a 1989 German edition, boxed set, published by Citadel under the name Sturmbringer."
Source: Wikipedia, "Stormbringer_(role-playing_game)", available under the CC-BY-SA License.