It seems to me there would be two ways to do Elric right:
1) Young Kingdoms D&D: Use the core rules as a base, do D&D conversions of everything you needed. Moorcock was one of the inspirations for D&D in the first place, so this is not as big a stretch as it sounds. It would be hard to simulate many specific things in the books with this method, but it would work well enough, and be compatible with other D&D stuff. (Although this sounds like what Chaosium tried, what they did was an ill-advised port of Stormbringer/d100 into D&D, and a lot was lost in translation).
2) Young Kingdoms D20: Make up your own version of the d20 system (like Conan or Black Company). This would be a much closer simulation, but much more work. It seems like much of the discussion here is trying to find the right combination of current systems (e.g. Conan with CoC magic tacked on) to do this.
I prefer #1, but I have always liked the young kingdoms setting while disliking most of the actual Moorcock stories set there. (Did the guy who played Elric have like the worst railroading DM ever, or what?)