The new South Africa goes on trial again this week. Twice.

On Monday, Oscar Pistorius returned to court to buttress his charge that this was a country so ravaged by crime that he had to arm himself to the teeth in expectation of murderous burglars.

On Wednesday, 25 million registered voters will go to the polls – the first since Nelson Mandela died in December and the fifth in our 20-year-old democracy.

Both events are being watched closely. Pistorius, who rose against massive odds to teach the world a new way of looking at disability, is an obsession for South Africa and the world. And as South Africa votes in a new government, the question niggles: where is the country heading? Can it fulfil its promise as a beacon of prosperity and progressive governance in the world?

This is one of those weeks where South Africa gives watchers across the globe their regular dose of its "one minute before midnight" scenarios: is this the tipping point?

Twenty years after Nelson Mandela cajoled, threatened and shouted down even his own comrades and led us down the path of freedom, his successor Jacob Zuma has been crisscrossing the country campaigning to be re-elected.

In answer to virtually every question, he trots out his party's election slogan: "We have a goooooood story to tell."

The masses imitate him, and so do the middle classes. But how good a story do we have to tell?

If there is one thing South Africans agree on, it is that our country is a far better place than the monstrosity it was before 1994. The fruits of freedom are numerous and real for many of us: a country where we walk proudly, without fear; a full citizenship of the world; a democratic dispensation and constitution to be proud of.

For the government, there is also much to trumpet on economic transformation, on access to health and education, and in relatively harmonious race relations.

For a black man who grew up under apartheid, it is unimaginable to even dare to compare: I grew up with stories of my father and my brother being arrested or harassed because they were in a "white area". We were not human under apartheid, we were a cipher. Now, my humanity and dignity has been restored and – as Archbishop Desmond Tutu once said – the humanity of the perpetrators has also been restored.

So as South Africa celebrates its 20 years of democracy the question is how much better could our story have been. The truth is that the shine is coming off our rainbow nation.

Every day now there are dozens of protests across the country over poor or absent services. Unemployment remains as intractable as it was 20 years ago (36% are out of work). The state of education remains parlous. South Africa is one of the top five most unequal societies in the world today. The economy is anaemic, growing at a mere 1.9% last year compared with averages of 5% across the African continent.

But the shine of the new South Africa really came off in the five years of Zuma's leadership, though. Corruption is rife, with the scandal of the president's private home receiving "security upgrades" of about £20m becoming the main motif of the election.

Other clouds loom. A pernicious secrecy law is awaiting Zuma's signature. The police are under the spotlight after the daylight killing of 34 mineworkers at the Marikana mine in August 2012. A handful of former ANC ministers have become so disgusted with their party they are calling on citizens to vote for smaller parties or spoil their vote.

As Thabo Mbeki, Mandela's successor, said in the early 2000s, South Africa is still a country of two worlds: the first rich and white, the second poor and black.

It is a reality every visitor to our country sees, and which ordinary South Africans are beginning to question. New political parties such as former ANC firebrand Julius Malema's Economic Freedom Fighters – which calls for nationalisation of the economy and expropriation of white land without compensation – are tapping into this disquiet.

A look back at the past 20 years is bittersweet. We have come so far, achieved so much, and yet have fallen so far short of truly transforming our country.

At an election debate, Congress of South African Trade Unions leader Zwelinzima Vavi, a fierce critic of corruption, told a minister who tried to defend Zuma's home improvements: "If you want people to believe in the future then you must be honest about the present."

The truth about South Africa today is that there are elements of a good story, as the ANC puts it. But that story is marred by how much better we could have been – and how much further we could have travelled – had we not allowed the twin evils of corruption and poor leadership to enter and settle into our political firmament.