Carnival Corporation controls with 45% the cruise market: cruise brands include Carnival Cruise Line, Holland America Line, Princess Cruises, Seabourn; P&O Cruises and Cunard in the United Kingdom; AIDA Cruises in Germany; Costa Cruises in Southern Europe; and P&O Cruises in Australia.
Royal Caribbean has a market share of 25% and has the following brands: Royal Caribbean International, Celebrity, Silversea, Pullmantur in Spain, and Azamara and has partnerships with TUI in Europe and SkySea in China.
Norwegian Cruise Line comes in third with a 9% market share: Norwegian Cruise Line, Oceania and Regent.
MSC Cruises has a 6.4% market share.
The remaining 15% is divided up by all other smaller cruise companies.
Most main stream cruise lines offer almost the same type of "american style" service while NCL specializes in "Free Style" cruising, eat where, with whom and at what time you want and no formal nights.
Some European cruise lines like Costa Cruises, have a more regimented style, when their cruises are mainly targeted to guests from continental Europe. This means no hot breakfast in the buffet section of the ship, no buffets at dinner time. No iced water with dinner, but water has to be purchased etc. If this is not your preferred way of cruising, please check before booking.