hawaii and its probably not really close. i say 'probably' because im hypothesizing based on logic, not experience.

best beaches in the US, best weather (if you like hot and dislike cold), probably some of the best food, probably the best people because its probably has the most 'foreign' personalities, probably the happiest people because of how great an environment it is (that type of thing affects joy way more than most want to admit), social life is probably very dynamic (like if you like day life you get that on beaches but if you like night life they have cities), i hear the water is actually warm and the rivers are awesome.

lots of other stuff too im sure. thing is that when living in US, i imagine you cant beat hawaii. i mean its where US residents go for vacation