Chung King is best, hands down, assuming they are as good as they were 2-3 months ago (the last time I was there). STH has a very limited menu of excellent dishes, and even these are way too greasy for my taste. Four Rivers is very good but I have never liked their restaurant's interior.
Yeah, the chef went to the new-ish Han Dynasty out in Exton. He moves around a lot.
My current favorite is Tasty House, but it doesn't have the 'ma la' that Chung King Garden does. Although I dunno...I had dinner at CKG a couple weeks ago and it wasn't quite as good as before. What's your favorite dish?