I have several of these:
I think the setting only really appealed to Moorcock fans, but I ran a gam of it probably 10 years ago that people still talk about ( not due to my super Gm skills, but because they were unfamiliar with the setting and really liked it once they were in).
The 2 main games are either Sttormbringer or Elric!
I've got the original Stormbringer and in that one, you end up summoning demons a lot to help you/ binding them into object, hence the magic in the world is very powerful, and (IMHO) you are dumb NOT to have bound Demon items ( armor, weapons, a servant, etc.). There were also more "modules" for Stormbringer through the various editions.
As For Elric!, the magic system worked differently. Meeting a low prerequisite, any character/class could use magic, but the magic was focused around them...so a Merchant would have magic that helps them identify and appraise, a Sailor had magic that helped related to voyages on the sea, etc. None of the magic was extremely powerful and I thought this added quite a bit to the game.
Both systems use Chaosiums BRP ( the percentile dice for skill check, combat, etc.). I like the system.
So what I do is I use Elric! as the basic rule set and to make characters, but take modules/adventures from Stormbringer.
~Desh