Tributes: George Best was "a football genius" who "gave pleasure to millions" around the world, the Taoiseach said.
Speaking in Hungary, Mr Ahern described the player as "one of my great sporting heroes" and "a man of great personal charisma".
He added: "Not only was he one of the finest footballers this island has ever produced, but he also one of the best players the world has ever seen.
"In the days ahead people will struggle with words to try to describe his talent. In this regard George should be remembered as the very best at what he did."
President McAleese paid tribute to "a wonderfully gifted sportsman whose skills on the football field dazzled a generation of soccer fans".
He would be remembered "as one of the world's finest football talents," she said.
DUP leader Ian Paisley prayed for comfort for the player's family, and said Best would probably never be bettered as a footballer. He was "unique in his football skills, a real magician on the football field, bringing delight to the multitudes of his fans".
Fine Gael leader Enda Kenny said that ever since Best's Manchester United debut "as a skinny 17-year-old", successive generations had recognised his genius.
"His balance, speed and toughness marked him out on the pitch. His skill and eye for a goal chance for himself or a team-mate made him truly special. Deadly with both feet, and surprisingly dangerous in the air for a slight individual, Best really had it all."
Labour leader Pat Rabbitte called Best "an inspiration to football fans in Ireland, North and South, and throughout the world". He had left "a remarkable legacy to Manchester United and to football".
"Tragically he also had some personal flaws that clearly contributed to his premature death," Mr Rabbitte said.
"However, I believe he should be remembered for his amazing skill, his charming personality, and the undoubted joy he brought to so many peoples lives."
Sinn Féin's Martin McGuinness said Best "brought immense pleasure to millions of people around the world".
Opening a book of condolence in Belfast, the city's Lord Mayor, Cllr Wallace Browne, recalled "one of the true greats of the footballing world - a tremendously gifted player".
He added: "His footballing talent proved an inspiration to generations of younger players, inspiring them to pull on their boots and follow their own dreams. I doubt we will ever see the like of his talent again."
DUP deputy leader Peter Robinson said Best would be remembered as probably the greatest football player of all time.
"He was a wonderful ambassador for, and provided much inspiration to, the people of the city and throughout Northern Ireland."
SDLP leader Mark Durkan spoke of his deep sadness at the player's death.
"George Best's great talent as a footballer is one of the main reasons why I, like so many others, support Manchester United.While he was undoubtedly a flawed genius, I hope he will be remembered as one of the greatest footballers the world has ever seen.
"For an insight into George Best's affable character, we need only look to the deep affection in which he was held by the medical support team that has been with him, not just in the last few years, but over recent years.
"The greatest tribute we can pay to George Best today is to remember the joy he brought to millions of people across the world through his skills."
Green Party leader Trevor Sargent praised the player's honesty in speaking about his alcoholism but said he would be remembered as "a man with a dazzling skill that lit up the lives of so many".
He added: "What was special about George Best was the way you could always sense the tingle of anticipation which would run through a football crowd when Best took hold of the ball. Only a very special and unique talent could instill that type of excitement and expectation."
Ulster Unionist Assembly member Michael McGimpsey said, "George was a sporting hero and inspiration for a generation, not just in Northern Ireland but across the world. He gave people a reason to be proud of Northern Ireland.
"George is a positive part of our past that we can look to when shaping our uncertain future. He symbolised the potential that this great province has yet to fulfil."