The 40-year-old Ethiopian, in his first appearance in Scotland, crossed the line in 61 minutes six seconds, a record for the annual half-marathon.
Three Scots finished in the first four of the women’s race.
Leeds-based Susan Partridge beat Freya Ross to the line, with Kenya’s Pauline Wanjiku third and Steph Twell fourth.
Olympian Katherine Grainger set the 23,000 runners under way from George Square in the city centre, with the start delayed by about 20 minutes.
Kenya’s Joseph Birech had been aiming to become the first man to win three successive Great Scottish Run titles but it was Gebrselassie, 28-year-old Bett and Moroccan-born Ayad Lamdassem, 32, who soon moved clear of the field.
Having led the way for the first 5km, Gebrselassie invited the others to take their turn at the front.
Bett accepted and only the legendary Ethiopian athlete could match his explosive break as the duo dropped Lamdassem on a route taking in many of the venues to host events at next year’s Commonwealth Games.
At 15km, the Moroccan was trailing by 25 seconds in warm conditions.
Gebrselassie, the world record holder at 20,000m and the one-hour race, surged 100m clear of long-legged Bett with a mile to go as they headed along the Broomielaw towards the city centre.
And he maintained the gap over the final mile to cross the line first at Glasgow Green.
America-based Andrew Lemoncello, who will represent Scotland in the marathon at the Commonwealth Games, finished sixth.
“Today was really wonderful. I am so happy,” said Gebrselassie. “It was a perfect set-up. I didn’t expect this kind of weather.”
Oban’s Partridge had looked a strong contender for the title, with her confidence buoyed by an excellent 10th-place finish in the marathon at the World Championships in Moscow in August.
She, Ross and Wanjiku set a brisk pace that ensured the trio were clear of the field.
Wanjiku was dropped as the three runners progressed along Paisley Road West in the city’s south side and Ross, back from injury, was next to struggle with Partridge’s speed as she moved 46 seconds ahead after 15km, with Wanjiku a further 54 seconds back.
Though she slowed in the closing stages, Partridge was never in danger of being caught and came home ahead of the field.
“I’m delighted to have won the race,” Partridge told BBC Sport. “Scotland should be proud of its distance runners.”
Maryport’s Simon Lawson won the men’s wheelchair race, which took place earlier in the day, while Sammy Kinghorn from Kelso took the women’s wheelchair title.
On Saturday about 3,000 children took part in Super Saturday events for families and juniors.
The Great Scottish Run was first held in 1982 and has grown each year, with 24,089 people taking part last year.