Something that's tragic a few millennia ago is likely still something considered tragic. War tearing a family apart (either directly or indirectly), for example, was a terrible thing in ancient Greece and is a terrible thing now.
Comedy, on the other hand, does not have such a long shelf life. Especially referential comedy. This fact is painfully obvious in Aristophanes' The Frogs.
Twenty pages into the play (about half way through the mystic bands' procession for Iacchus (a.k.a. Dionysus)), almost all of the jokes have been references to other plays or playwrights. If we still had copies of the latter and full biographies of the former, maybe these jokes would still work. But most of them miss their mark entirely.
That said, I can see where a few of these referential jokes are going and do get a smirk out of them, but for the most part they're lost on me.
However, one style of joke that never seems to get old is the laugh at the audience's expense. I'm reading this play in its "Digireads.com Classic" edition (a few minor typos make this text's being in the public domain quite clear), so the joke in question is on page 21. It runs thusly:
"DIONYSUS: [asking his slave about the spirits the ferryman Charon says inhabit the perimeter of the lake of the damned.]: But tell me, did you see the parricides and perjured folk he mentioned?
XANTHIAS: Didn't you?
DIONYSUS: Poseidon, yes. Why look! (pointing to the audience.) I see them now."
Reading it didn't get me to chuckle, but I did crack what I imagine is a wry smile.
Hopefully I'll find something that's got even more kick left in it over the next sixty pages, and get a really good laugh.