Kiir and al-Bashir addressed a crowd of tens of thousands of people who gathered in south Sudan's capital Juba for the event.
In a long and critical speech, Kiir said: "The [deal] ensured a radical change in Sudanese politics [and] equitable and transparent share of wealth and resources. Has this happened? The answer is incredibly no!"
Al-Bashir said not all the blame lay with his National Congress Party (NCP) and that the former southern rebel Sudan People's Liberation Movement (SPLM) was also responsible for delays.
"For six months we waited in Khartoum for our brothers in the SPLM to come," he said in his speech. "In the end we paid $60m for these people to come."
Sudan's north-south civil war killed two million people and drove more than four million from their homes, sparking refugee crises in neighbouring countries.
It also exacerbated a rebellion in Uganda as the Lord's Resistance Army (LRA) rebels sought refuge from Kampala in lawless south Sudan.
Sudan's civil war broadly pitted the Islamist Khartoum government against mostly animist Christian rebels, complicated by issues of oil, ethnicity and ideology.
The 2005 deal formed a national coalition government, a semi-autonomous southern authority, and ensured power and wealth-sharing.
Separate north and south armies were formed and the south can vote on secession by 2011.
Yasir Arman, the SPLM's deputy secretary-general for north Sudan, warned this week that failure to fully implement the accord would lead southerners to vote for independence.
Sudan's oil wealth, its output of 330,000 barrels per day of crude accounts for more than half the nation's budget, forms a key part of the agreement.
But the dominant NCP continues to reject an independent commission which under the deal determined Sudan's two main oil fields are in the south.
It has also not agreed on a border demarcation which would determine whether the oil belongs to the north or the south.
|"These will be reasons for war in case the majority of the people of the South will choose in favour of independence"|
former UN envoy to Sudan
Jan Pronk, a former UN envoy to Sudan, said on his web log in December: "These will be reasons for war in case the majority of the people of the South will choose in favour of independence."
Kiir also accused the northern Sudanese Armed Forces (SAF) of continuing to support the LRA and other armed groups, saying it was alarming.
He said support from the SAF to militias in the south caused clashes between the north and south Sudan armies in the town of Malakal late last year which killed 150 people.
Al-Bashir said the government had dealt with 30,000 of the 40,000 militiamen in the south but said that such a large job could not be done overnight.
Raphael Tuju, Kenya's foreign minister, expressed concern that the peace deal could derail and said a regional conference should be held as soon as possible in Nairobi to address the problems.