Our flight is arriving at 5:30 PM on a Friday. With passport control, baggage claim and customs and the cab to central Athens, when might we expect to arrive at our hotel? Providing the flight is on time, what is the best case scenerio and the worst?

With passport control, baggage claim, customs and heavy Friday evening traffic you can expect to reach the hotel in 2-2.5 hours after you land.

Thank you, brotherleelove. I knew I could count on you for an answer.

Where are you coming from and is it a direct flight.
We fly transatlantic to Frankfurt and connect on a flight to Athens from there. In that case you clear EU passport control in Frankfurt and there is no passport review in Athens so you walk straight from baggage into the arrivals level of the airport and away you go.
We also travel ultra light with small carry on back packs only, so we walk right past baggage and head into Athens.
This will reduce your time in the airport. Now for Athens rush hour traffic, that's always going to be slow.

I'll be going Dallas, Madrid, Athens. Thanks for the reminder about the EU and flights within Europe.