We went to St. John last year on our honeymoon, and it was wonderful. A largely unspoiled island with plenty of isolated beaches, rainforest areas, and big mountains. I don't know of any all-inclusive plans there, but that doesn't mean there aren't any.
Somewhat more commercialized, though still very nice, is Aruba. All-inclusive plans abound there. It's more of a desert island, though, with 85 degree temps, "divi" winds and no rain 10 months out of the year. The sun is hot, the sea is warm but refreshing, and getting rained out is all but unheard of.
I'd go back to either island in a heartbeat.