Perfect blend of location and friends. I went to St. Lucia a few years ago with some friends. We were a unique assortment of friends who just totally clicked that vacation. Gorgeous nights looking at the stars and chatting about random things. Daytime excursions where everyone's rhythm just match each other's. Amazing scenery. Scuba Diving.

So I'd say my perfect vacation must include these things:
Camraderie
A dose of solitude
Close to Nature
Starlit skies
Discovery of new places and culture.
Weather ideal to the locale.