I would have picked the same top three the Bruce identified - probably would have flip flopped Carnival and Royal. And wouldn't disagree with Marc's comment above. Seems the less passengers pay for a cruise the more they try to save on other expenses.
A Bad Day At Sea [with power] Always Beats A Good Day At Work
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014, Regal 2014
Star Clippers: Royal Clipper 2015