I don't know if I really have a favorite. The Caribbean hasn't lost it's luster for me, I still love to sail there. I wish I had chosen a Caribbean cruise over my upcoming Mexican Riviera cruise on Carnival, but I wanted to sail on a Carnival Spirit Class ship.
If I had to chose a favorite, I guess it would be the US Virgin Islands. St. John to be exact, most beautiful Island I have ever been on! Although the government there really needs to fix and clean the public restrooms on St. John though.
I also enjoyed Belize a lot and Barbados. The French side of St. Maarten is really nice too.