The entry requirements to be a Brotherhood leader is 2 skills over 110. Companies, Colleges, Gangs and Regiments are given as examples of Brotherhoods and I would expect to find multiples in a large city. This seems like a level of skill much more common than "best in the world".
I looked again through my copy of Runequest 6 and I couldn't actually find anywhere with guidelines on what each skill level mean within the book so I don't know what your basing your estimations on. I guess we just interpret the book differently then.
"O happy dagger!
This is thy sheath; there rust, and let me die."
- Juliet Capulet
So then "one of the best in the world" should be around 120? That would mean starting characters should be able to have at least 80 to 90 in a skill if they specialise, since that'll be the professional level I guess? I think the main point is that characters in their early 20s should be able to have a highish skill level in a skill if they specialise in that specific skill. This would represent above average, but not truly exceptional people.
As I said, not every game needs to be about those people. It's just that they are not too far fetched in other systems.