The 21-year-old racked up 22 points to see off Vladimir Tuychiev of Uzbekistan (18) while Ilya Chernyshov of Kazakhstan (17), gold medallist in the team road time-trial, took bronze.
The big disappointment was pre-event favourite Makoto Iljima of Japan, as the 35-year-old recently anointed Asian champion failed to medal, finishing fourth with 10 points.
The gruelling 160-lap race over 40 kilometres and 16 sprints was dominated by Cheung who admitted he hadn't expected to win but grew more confident as the race progressed.
“I did exceptionally well,” said Cheung, who was third in the points’ race at the Asian Championships in Kuala Lumpur.
“I was pretty nervous and didn't expect gold but the more I saw that my rivals were struggling the more my confidence grew.”
Tuychiev could not believe he had secured silver, especially with the meagre resources the Uzbeks managed to cobble together just to get their team here.
“A sponsor? What's a sponsor? We don't have such a thing,” he said.
“We have mum and dad and they buy us a pair of shorts if we're lucky.
“If there's a sponsor out there who feels like us giving a call, we're waiting.”
The 23-year-old also made a plea to the national sport's federation to spruce up their act and start supporting their cyclists.
“Maybe after this medal they'll start to develop it,” he said. “We have an old rubbish tracks so we train on highways.
“Today (Wednesday) we raced on bikes borrowed from Moscow and they're old models as well. We just don't have $10,000 to spend on a bike.”
Chernyshov was in no doubt how important his medal was to his country and his sport.
“I guess I saved track cycling for Kazakhstan,” said Chernyshov, whose discipline suffers in his country in comparison to road racing.
Tour of Spain champion Alexandre Vinokourov managed to persuade a group of Kazakh businessmen last summer to stump up the cash for a new team called Astana after his previous one was embroiled in a drugs scandal.
“We knew before we came here that without medals, we wouldn't get sponsorship. This was important.”
The other track medals on Wednesday went to form with China's dual bronze medallist from this year's world track championships Guo Shuang winning the women's sprint, beating compatriot Gong Shinjie.
It gave China their sixth gold in the event in six Asian Games.
The men's sprint went to Japan's Tsubasa Kitatsuru.—AFP