I quite like the look of the old CDG terminals, nothing but proper modernist traffic machines. Shame it's a ballache to get through the airport though. Heathrow terminal 5 is quite decent for a big airport, but can't stand the rest of the mess that is heathrow though.
I prefer leaving airports, rather than arriving though. So in that sense, probably Changi airport. It is nice to get off a plane after such a stretch.