The show, which charts the turbulent life of the football genius - from his childhood on the Cregagh estate to a life of fame and controversy - is written and produced by Belfast playwrights Marie Jones and Martin Lynch and composed by Scotsman JJ Gilmour.
"Initially I thought no, I don't want to write this at all," Marie Jones told UTV.
"But when I heard the music I thought, well, if we don't do it somebody else will and it won't be right and from here.
"I'm from east Belfast - we should be the people to do this, so let's get in there and do the best we can, and make a great tribute to him."
Aidan O'Neill, a Tipperary-born actor brought up in Tyrone, plays the role of the soccer legend.
A number of well-known local actors including Conor Grimes, Packy Lee and Maria Connolly also star in the musical comedy.
Martin Lynch reflected on the year and a half of hard work which had gone into putting the show together.
"It's the end of a long and hard 18 months for us, and it's exhilarating to be here to watch the whole thing come together on the stage," he said.
"I think the audience are really loving it."
Julian Glover, the English actor famed for his roles in Star Wars: Episode V and Indiana Jones and the Last Crusade was also in attendance of the opening show.
He had high praise for the cast.
"It was absolutely brilliant, an exact compilation of his life done very simply," he told UTV.
"The performers - well, there's not one in there you could fault."
Legends remembered
Another Northern Ireland sporting great, Alex 'Hurricane' Higgins, was also remembered on Wednesday night with a minute's round of applause at the finale.
The 61-year-old was found dead after a long battle with throat cancer and alcoholism at the weekend.
"The introduction of 'Hurricane' Higgins at the very end was wonderful," Julian continued.
"The whole poignant thing of them together - the two great working-class men who produced a fantastic history of sport - was beautifully done. Very moving indeed."
The show runs until 14 August and the official red carpet premiere takes place on Saturday night.
Famous guests - including former Northern Ireland and Manchester United goalkeeper Harry Gregg, a host of fellow Man Utd legends, Sir Matt Busby's daughter Sheena, golfer Ian Woosnam and actor Sean Bean - will join family and friends at the charity event at Belfast's Grand Opera House to support the George Best Foundation.
In notes for the programme, Gregg revealed he once threatened to break Best's legs after he put the ball past him too often.
The mercurial teenager knocked the ball through the goalie's legs twice during a five-a-side game while still on trial with Manchester United in 1962.
"He was one wee slip of a kid and I remember his piercing blue eyes. I was in goals and he managed to get the ball in between my legs," Gregg said.
"My first thought was 'I've slipped', but really I thought it was a fluke. Within a matter of minutes it happened again and I said to him: 'Do that again and I'll break both your legs!'
"It turned out to be the beginning of a great friendship that spanned many years. I miss him badly."
Best died in November 2005 after a long battle with alcohol abuse.
Gregg added: "George was a bright and shining star, but I didn't know that that star was to burn out so quickly.
"The word hero is much overused but in the case of Best it is very apt. George was a genius on the pitch, it was his domain. It is my personal belief that it was off the pitch where his coping mechanism failed him."
Sir Michael Parkinson was to have been a special guest of the foundation, but has had to withdraw for family reasons. However, a DVD message from him will be shown at the after show reception.
Sir Michael was a close friend of George and author of Best: An Intimate Biography.
A DVD from Eamonn Holmes, the foundation's president, is also expected to be shown at the after show reception.
Broadcaster Gerry Kelly will host an auction.
Barbara McNarry, George Best's sister and secretary of the foundation, said: "All funds raised will be invaluable in helping the foundation promote a healthy lifestyle for young people through football and other sport-based initiatives."
Part three of the documentary following the making of the musical 'George Best, From Football Boots to Dancing Shoes' can be seen on UTV next Tuesday.