The train ride into HK is not very scenic. It takes 24 mintues from the Airport to Hong Kong Station. There are a number of express buses that go into Central that you get to see a lot more on. They are express, but still take about twice the time of the train. You could take the train into Central, then go up to the Peak to get the ultimate view over Hong Kong. You can do this buy bus, taxi or on the Peak Tram.
Alternatively, you could go to Tung Chung, which is just near the Airport and go on the Ngong Ping 360 cable car up to the buddha.
What to do all depends on what time of the day you are arriving and how much pollution is around.