In all of Hong Kong, or the HKDL Resort?
The best restaurant at the resort would probably be the Crystal Lotus, serving Cantonese cuisine. The best restaurant in the entire city would be a much harder suggestion for me to make, considering I have only tried a handful. Plus, it depends on what cuisine you favor the most. Many of the best restaurants in the city are located in the posh, 5 star hotels.
The Peninsula Hong Kong is one such hotel that contains a plethora of exceptional restaurants. Gaddi's is widely regarded as the best French restaurant in Asia (definitely the most elegant), while the Spring Moon serves some of the best authentic Cantonese cuisine in the city.
Bear in mind that the Peninsula is also probably the most expensive place in Hong Kong, but from what I've heard, anything in it is excellent. The Mandarin Oriental's food is pretty good too, if a bit pricey.
I think the best restaurant in Hong Kong must be the yung kee restaurant in Hong Kong island, a few blocks from Central. Its food is very authentic and delicious, and it's reasonably priced. http://www.yungkee.com.hk/ Always try the duck or goose.
If I remember correctly, there are 2 Mandarin Orientals very close to each other in Hong Kong. The original and I believe flagship of the chain is the better of the two in my opinion. Better restaurants and better atmosphere, though the contemporary look of the Landmark is quite attractive.
Another favorite hotel of mine to dine at is the Island Shangri-La. Great restaurants, especially Restaurant Petrus. And it's a very nice hotel too, one of my personal favorites to stay at.
I'd second godisender's recommendation of Yung Kee. Reservations are a must!
Mickey D's in Kowloon.
I highly recommend Bubba Gump. It's a pure American restaurant set in a pure american atmosphere. It's located atop the peak, providing the best views. It's food is also not very pricy, it's affordable high-quality food.