I did this before but, just counting this season, guys who are playing better than Rondo (in no particular order):
CP3
Westbrook
Parker
Curry
Lillard
Irving
Wall
Lowry
Teague
Bledsoe/Dragic (not sure who is actually the point the majority)
Derrick Rose
Deron Williams
After that names like Collison, Brandon Knight come to mind, but I'd feel gross putting them on the list.
One difference between Rondo and all the PGs on the list above (with the exception of Parker) is that he was the starting PG on an NBA championship team. Also a Game 7 NBA champ runner-up and a Game 7 ECF runner-up. He has a better resume with star talent around him than any PG above other than Parker.
This leads me to only the conclusion that if I am a GM with talented players (or the prospect of getting other talented players), Rajon Rondo has a lot of value. It doesn't matter where Rondo ranks compared to other PGs (inexact as that is), it matters how valuable he is to us or to another team -- and I think that value is pretty high.