I've been twice in Ephesus: the last one as part of a circuit across Anatolia, the first one in a short visit coming from Greece.
I was in Samos and found that it was available a day tour to Ephesus, and Selçuk.
We did it and enjoyed. So, if you want to see Ephesus in a glimpse, and rather stay in Greece, this trip is easy and cheap (from Samos, not from Athens, of course!).