"I'm an Australian," Williams told the Herald Sun. "Nothing makes up for missing out on the Melbourne Cup."
Williams also paid tribute to trainer Mikel Delzangles and owner Sheik Fahad al Thani for coming back to him with the winning ride.
While Dunaden wasn't the top choice of Hong Kong punters, his effort did not surprise his jockey.
"I was so confident after riding him in work on Tuesday," he said. "He was actually in better condition here than he was in Melbourne."
As welcome as the victory was for connections, it may have cost Dunaden a chance at the second Melbourne Cup his owner and trainer had hoped for.
Dunaden carried 54.5kg in this year's Cup and having won it and now been successful at weight-for-age in another group one, he may well be weighted out of next year's event.
But for now, Sheik Fahad and Delzangles are in favour of a return to Melbourne.
"Nothing is decided for the long term except that we want to go back to Australia," Delzangles said.
"In the short term he is having a big holiday."
Dunaden showed surprising speed from the gates allowing Williams to position him perfectly for the first 2000m. But as the field bunched 400m out he found himself pocketed.
"I was very worried at that point, but when the gap came this great horse just went for it," he said.
"He's a champion, a real champion."
In the other international races, California Memory won the 2000m Cup, Australia's Brett Prebble saluted in a tight finish on Lucky Nine in the 1200m Sprint and Able One captured in the Mile. Kiwi Jimmy Choux weakened to ninth after having every chance.