Mediterranean cruise advice .?

Another shout for Cruise Kings, very good company who will look after you. Take the drink/tips package and upgrade to a cabin with balcony. We stayed 3 nights in Athens and then sailed around the Greek Islands on Norwegian Jade. Stop overs included Rhodes, Mykonos, Kephalonia and Santorini. A very good cruise for our first time!
We have just done a Mediterranean cruise with TUI nothing wrong with it but not for me and the wife, we boarded in Tenerife sailed for Gran Canaria, 8 hours in port then we went to Maderia overnight at sea all day at sea overnight at sea 8 hours at port then off to Modril over night at sea all day at sea overnight at sea. This continued to Palma then Calgri ,Valetta and finally Corfu where we flew home.
There were loads of people who had done 20/30 cruises even returning to the same ship. Personally, I wished we'd stayed in Tenerife.
Marella cruises are a good starting point. Usually all inclusive decent itinerary and the ships are fairly laid back. Best cruises we have done though are with Royal Caribbean.