From 30,000-ton converted transatlantic steamers carrying a few hundred passengers to 225,000-ton vessels carrying 5,400 guests; from small inside cabins to exclusive duplex suites; from one or two main dining rooms to dozens of eclectic culinary venues, including celebrity chef signature restaurants; from shuffleboard and ping pong to wave riding, waterparks, rock climbing, bowling and ice skating; from tiny windowless gyms to 20,000-square foot luxury spas: Cruising is not what it used to be.