I've been on three Caribbean cruises, and have never been back to any of the 20 or so islands I visited, not because I didn't like any, but because what you see in a four hour excursion isn't always enough to allow you to decide between them.
Funnily enough I've done the exact opposite, eight years ago I stayed in Margarita for 2 weeks, and I only enjoyed the holiday for what it offered in excursions Off the island, e.g trips to Angel falls, Los Roques etc. I wasn't that impressed with Margarita itself, but I wouldn't have missed it because of those excursions.Three years later I called at Margarita for a day as part of a cruise, swam with dolphins and based on what I saw that day, I would never have chosen Margarita for a prolonged holiday, and hence missed out on two of the most memorable excursions of my life.

I have been to a few places when a cruise docked. The one I will remember most is Antigua. We had a stunning beach which was so long you could find a spot with no-one next to you. One morning we arrived and for thelife of me it was another beach. Row upon row of sunbeds anf also loads of locals selling things and not giving you pesce. Those cruise folks really had no idea what the beach was teally like.