I was discussing this on another forum, where I used the term incorrectly as "supergroup".
A supergroup is actually defined as a group of singers who are already popular in their own right.
So what proper term would be used to describe a group that had achieved the level of world wide popularity that only a few groups like Queen, Led Zeppelin, the Beatles, have done.
I agree with all of the replies, but there is a term that describes some of the huge groups like Queen, but its not "supergroup".
As in Queen was one of the premiere "supergroups" of the 70's.