"I think if we had the good fortunes of Mandela for two terms, we would have had a better chance because he was a committed democrat," said Ramphele, a onetime anti-apartheid activist and a former World Bank managing director, on Thursday.
"I'm not so sure that his successors are committed in the same way that he was."
Ramphele is preparing formally to launch her new political party Agang, which will challenge President Jacob Zuma's ANC in polls next year.
Ramphele made the announcement at a Foreign Correspondent's Association of South Africa meeting on Thursday.
Agang was formed as a party political platform in February, but will now become an official political party.
"We are supposed to get our registration certificate this week," the struggle icon and organisation leader said.
Areas of concern she cited included human rights, weak schooling and health and police brutality.
'Journey to democratic politics'
South Africa has had difficulty making the transition from the culture of liberation that fought the white minority apartheid rule to an effective democracy, she argued.
"The journey to democratic politics is a journey we didn't as a country understand we needed to undergo," Ramphele said.
The ANC has ruled since the fall of apartheid in 1994 with overwhelming victories at the ballot box but is under pressure because of failures to deliver on promises.
"What is discouraging is the sense of resignation that so many people feel," said Ramphele. "What's going on is bad, but people don't seem to see an alternative."
After nearly 20 years of democracy, the country was "on a completely wrong track", she said.
"There is no doubt that looking at where South Africa stands, nearly 20 years after that beautiful day in our history, we are a country which has not lived up to the promise of that dream." – AFP