After doing some digging and reading the material I found I think that GNS/GDS as a tool for analyzing RPG systems is a little broken. As a tool for analyzing player style/desires it's pretty good. But reading about that led me to the WotC survey in 1999 (with online summaries
here and
here) which looks to be more useful still, particularly the first link.
I would guess the most successful streams are the most story oriented (other significant factors have to come into play but I'm not even going to attempt to list them) because those are the closest to traditional media and the most accessible for observers/watchers.