Fodors provides the advice on the website listed at the end of this column, from which I have excerpted the following.
For Families. Cruise ships with trained youth counselors and the most extensive facilities for children and teens, plus parents and grandparents include: Carnival, Disney, Holland America, Royal Caribbean, and Norwegian Cruise lines.
For Romantics. Smaller ships with intimate lounges, such as SeaDream Yacht Club, Windstar Cruises, and Royal Clippers are the favorites of many couples.
For Sports Fans. Royal Caribbean can’t be beat for on board sports; each ship has a rock-climbing wall and sports courts, while some have miniature golf courses, roller-blading tracks, and ice skating rinks.
For Water Sports Enthusiasts. Snorkelers and divers rate Norwegian and Princess Cruise lines highly for their organized tours and diving instruction programs. Small ships with retractable marinas offer the opportunity to sail, windsurf, and water ski from the comfort of your ship.
For Foodies. The importance of cruise food can’t be overlooked and the hottest dining experience at sea is found on ships with specialty restaurants. Some feature regional cuisines, such as the highly rated Italian and Asian restaurants on Crystal Cruise Line ships. Others, like the fleets of Princess and Holland America, have upscale steak houses that serve the highest quality cuts of beef available.
The following website has much more on this subject, including cruise ship categories that would be very helpful as you decide what is best for you. I highly advise you check it out before making your decision.