I know this is not the answer that you are looking for but I can tell you two things I like to listen to:
#1 a stream that sounds good.... decent audio levels and most importantly no channels that have annoying static every time they come active-
#2 a feed that does not have so many busy channels on it that is perennially impossible to completely follow anything happening on it-
When I go looking for new feeds to enjoy, quantity is not as important as quality... sometimes I will listen to 10 low activity feeds at a time and if one of those feeds has a channel that is very staticy, it drowns out all of the other feeds while it is active and is just annoying in general..
Sometimes I listen to busier feeds, but once again, nothing is more frustrating than trying to listen to a stream that is so jam packed with action heavy channels that when you do hear of something exciting, it is impossible to follow along because you are are constantly missing many key transmissions...
Granted, practically every feed that is actually scanning is going to have periods of high activity and missing conversations is inherent but when evaluating new feeds, If I come across a stream that has either of those two conditions, I blacklist that particular feed because I find it too annoying to listen to...
As for feed content, I only like to listen to public safety on feeds. Dont get me wrong though, I have a radio at home that scans rail, utilities, air, hospital security, taxi, road crews, wrecker services..etc but when it comes to feeds from outside of my reception range, the only thing I care to hear is public safety calls. mostly fire, rescue and law enforcement...
I also think dedicated air band feeds are cool but I don't like them mixed in with public safety.