Two-time Tour de France stage winner Robbie McEwen of Australia said he could never forgive Armstrong, adding he "deceived everybody on the planet, us included."
World Anti-Doping Agency president John Fahey told The Associated Press in a telephone interview that Armstrong's assertion in his interview with Oprah Winfrey that he wasn't cheating when he took part in doping through his seven Tour de France wins "gives him no credibility."
Top-ranked tennis player Novak Djokovic was even more succinct in his judgment, saying at the Australian Open that Armstrong "should suffer for his lies all these years."
Story Continues Below Slideshow..
Veteran cycling commentator Phil Liggett hopes Armstrong divulges more detail of his doping operation in the second instalment of Winfrey's two-part interview.
"He's gone halfway, he's told us he took drugs, he's told us how long he took drugs. He swears categorically he's never taken drugs since '05, since his comeback period. But that's all behind us now," Liggett told Australian Broadcasting Corp.
"Where did he get the drugs from? Where did all the big money go to pay for those drugs? Because it's very, very expensive to buy EPO. Who gave him the knowhow, the wherewithal to do it?"
Journalist David Walsh, whose articles and books had detailed the American cyclist's use of banned substances, agreed the interview did not go far enough in revealing details of his actions.
"He has to name names ... he is probably the biggest cheat sport has ever known," Walsh said on the BBC.
However cycling's governing body, the UCI, welcomed Armstrong's confession, saying in a statement it was "an important step forward on the long road to repairing the damage that has been caused to cycling and to restoring confidence in the sport."
McEwen, speaking from Adelaide ahead of the opening WorldTour event, the Tour Down Under, said he was just as deceived as the public.
"We wanted to believe, like everybody, that the Tour (de France) was clean. We're all athletes out there suffering through the mountains and you like to think he was just training harder and working harder than we all were," McEwen said.
Armstrong said in the interview that he "looked up the definition of cheat ... and the definition is to gain an advantage on a rival or foe. I didn't view it that way. I viewed it as a level playing field."
Fahey said that rationalization was not plausible.
"He was wrong, he cheated and there was no excuse for what he did," Fahey told The AP. "If he was looking for redemption, he didn't succeed in getting that."
McEwen also rejected Armstrong's justifications of his actions.
"The problem with people like Lance, or any other drug cheat, is that they think everyone else is doing it so they have to do it," he said. "In fact not everyone else is doing it."
McEwen was heartened that Armstrong's explanation of how he evaded detection for so long is a feat difficult to replicate in today's anti-doping environment.
"One of the big changes that have been made is the introduction of the biological passport and the whereabouts system, and that has made it, I would say, virtually impossible for this kind of thing to happen again," he said.
Fahey said that there was no doubt that drug testing had improved markedly since Armstrong won the 1999-2005 Tours. Armstrong retired for two years before making a comeback in 2009, and the WADA code for drug testing adopted by most countries was instituted just before the 2004 Athens Olympics.
"Some of them (drug tests) may have been ineffective back then, but that has changed," he said.
Many of the teams gathered in Adelaide remained tight-lipped as they digested the interview and its implications. Most riders and team directors contacted by the AP generally refused to comment.
Armstrong's former mechanic and personal assistant, Mike Anderson, however, who had to battle legal action after accusing Armstrong of drug use, couldn't bring himself to watch Friday's interview.
Texas-born Anderson settled in New Zealand after being fired from Armstrong's personal staff in 2005. In 2010 he told Sports Illustrated that while helping Armstrong clear out an apartment he shared with his former girlfriend in Spain he found a box labelled Androstenedione, a banned steroid.
"I don't want to waste any more of my time with Lance Armstrong," he said. "He's an incredible actor and that's what you (saw) today on the Oprah Winfrey show."
Former Armstrong teammate Stephen Swart, who was one of the first to blow the whistle on Armstrong's doping and was also attacked by the American's legal team, was unimpressed with Armstrong's claim in the interview that he never pressured team members to engage in doping.
"If he didn't say it then it was coming through the team management," the New Zealander said. "They were all on the same program."
Stuart O'Grady, a 2004 Olympic gold medallist who has worn the Tour yellow jersey twice, said while he was disappointed and let down by Armstrong's actions he was hopeful the confession could be a healing influence for cycling.
"As much as it's been shocking for the cycling world, it's cycling that's suffered for years so hopefully through Lance's confessions we can start looking to the future and something good can come out of this," O'Grady said.
"The damage has been done, but what we can do now is look to the future. ... It's a great sport. It's our lives, not a hobby and it isn't going anywhere."
Djokovic said Armstrong's admissions meant he had "lost a lot of faith in cycling."
"It's a disgrace for the sport to have an athlete like this," Djokovic said.
"He cheated the sport. He cheated many people around the world with his career, with his life story. They should take all his titles away because it's not fair towards any sportsman, any athlete. It's just not the way to be successful."
Djokovic's opponent at Melbourne Park, Radek Stepanek, was just as damning.
"I don't think it's an excuse, that 'I was doing it because everybody was doing it.' I don't think it's an honest thing," Stepanek said.
"If you want to do it, then you know that it's cheating. You know that you're cheating. And you have to live with it, which is the thing, for me personally, I don't understand because I wouldn't be able to live with it."