More itineraries with two and three day visits to places that warrant them. The Caribbean excepted, the once-over-lightly treatment can be a real problem in the "so near and yet so far" sense. I always shake my head at one day stops in Rome, for example, where it's a couple hours on a bus each way to the city--leaving maybe four hours to "explore," most of which is spent in traffic jams.
The cruise lines' emphasis on "quantity"--how many ports can we squeeze in, instead of "quality"--how can we help people really appreciate the important historical and cultural centers of the world, is a big downside of cruising.
But it's also clear that these itineraries are the product of massive amounts of research which are obviously dictating the "one day stand" approach. It's an extension of our soundbite culture, I suppose.