I remember flying from New York to Tokyo as a kid. 747, on the order of 14-15 hours as JFK-Haneda on a 777-300ER runs 13 hrs 50 min even now.
DEN-NRT is a bit more palatable at 11h 45m. Too bad there's no DEN-HND non-stop.
747 is still the fastest commercial airliner out there.