Should I take one of the island hopping cruises in the Greek islands, stopping at about 4-5 islands over a 4 day period. Or should I just stick to 2 islands, e.g. Santorini and Crete?
There really is not an answer to that question. What is your preferred style of travel?? Lots of quick hit or slow and easy. What time of year are your traveling? And it is not either or. If I had just four days, I would go to Santorini or Mykonos and enjoy that island.
I've looked at the cruises that you are speaking about. In my opinion they are squeezing too much in a short period of time. I would concentrate on two or three. Just two if you are thinking Santorini & Crete since they are fairly far away from each other, maybe three if you stay in the Cycladic chain (for instance, Santorini, Paros, and Mykanos).
Rhodes is beautiful, as is Patmos, Corfu and Crete. Have a great time!
If all you want is a brief glimpse of souvenier shops for a few hours each on 4-5 islands then take the cruise.
4 days total for 2 islands? It takes at least a week with a rental car to explore Crete, and even then you'll just be scratching the surface.
If you only have 4 days then choose one island and stay there long enough to decompress, enjoy your surroundings, and get into the rhythm of island life.
Joan - The answer to your question - Santorini and Mykonos - The two most popular Greek Islands of over 220 Islands. A couple of days on each Island will show you just how spectacular they are.
Enjoy, Greg