If it's this itinerary:

Piraeus - Kusadasi - Kos - Bodrum - Rhodes - At Sea - Dubrovnik - Venice

versus this itinerary:

Venice - Dubrovnik - Kotor - At Sea - Santorini - Kusadasi - Mykonos - Istanbul

It's a hard call--Bodrum would be cool, so would Rhodes (and probably Kos, perhaps a little different than Mykonos). On the other hand, everybody loves Santorini, and of course Istanbul is amazing.

Or this one:
Piraeus - Mykonos - Nafplion - Corfu - Dubrovnik - Koper - Venice

Nafplion is really cool. Don't know about Koper (edited to add: I looked it up, it's in Slovenia, very close to Italy. It looks great.)