> Show me a convincing example of something that's simple/clear/elegant/superior in Lisp, and how difficult/complicated/ugly/impossible it would be to do the same thing in Java/C++/Ruby/Python.

Serialize and deserialize data. You're currently using something like XML or JSON for a human readable data serialization format in those languages. JSON and XML are not first class components of those languages. S-expressions are a better version of JSON and are first class components of Lisp.