The YouTube account Luminist has been posting his synth covers of the Metroid soundtrack for the past few months and it is really, really good stuff. He posted the final track at the end of last year but it really is worth listening to the whole thing
Tracks like Tourian sound like they are straight from a John Carpenter soundtracks and the final fight with Mother Brain is just an incredibly tense mash of sounds. You can find the whole playlist here.
Oops, sorry about that!