Palau, Komodo, Borneo all get my vote.......as does Jupiter, Florida (but Jupiter is easy peasy diving....just really nice).
As for the best ever.....I've just come back from Truk and am still blown away by the most amazing diving diving I've ever done. My video is nearly done and hopefully will do it justice. Intact engine rooms, weapons, massive ships.......everything oh wow. Normally I'd limit my films to 4/5 minutes but I don't care after Truk. It's gonna be 9.5 mins and I'll love every second!!!
Andra and Baloo were there at the same time and can surely confirm to it's awesomeness!!!