Great subject, tough call.
I was in Alaska when I was a little kid -- it's a beautiful place. If you've never been and you get an opportunity to go, do it!
As far as just pure excitement, I guess it's a tie: New Orleans/New York City/Cancun.
As far as the mile-high club: I'm not a member, and while I'd not be against joining
I think there must be plenty of other places that would be more exciting.
As opposed to the "mile high" club, I am a member of the "beach" club. Any others want to 'fess up to the sun (or moon, no pun intended), the sand, the waves, etc.?