"I hate watching myself on screen but I love playing James Bond," Daniel Craig said on the red carpet at London's Royal Albert Hall, where he was joined by co-stars Monica Bellucci and Lea Seydoux.
"There's different sides of his character that we explore in this," he added, who was in black tie.
He added that the film was intended to honour Bond classics while trying to "freshen everything up."
Sam Mendes, who won an Oscar for American Beauty in 1999, said, "We sweated blood over it and I'm really, really thrilled and a little bit relieved".
When asked about what it felt like to be a 'Bond girl' -- a term that is sometimes seen as patronising towards the actresses who play the roles - Lea Seydoux smiled and said, "I don't know if I'm a Bond girl, I'm just a blonde girl."
The French actress, who wore a gold lame dress, plays Madeleine Swann, the daughter of a former Bond villain.
Italian actress Monica Bellucci, reportedly the oldest ever Bond girl at 51-- plays Lucia Sciarra, a criminal's widow who warns Bond off his dangerous quest.
Ralph Fiennes, who plays Bond handler and loyalist MI6 chief "M", said it was 'a very well-crafted film.'
"It has great energy and forward momentum," he said.
The film begins with a final mission set by the previous M, played by Judi Dench, and sees a haggard-looking Bond shaken, not stirred by his past.
Bond early on in the plot brushes off a question about what he would do if he was not an assassin, but spends the rest of the film working it out.
Along the way he faces his chilling nemesis, who wears a collarless Nehru jacket like in classic Bonds past but has a data-driven domination mission with a contemporary ring to it.
Daniel Craig said he had been 'desperate' to face the shadowy organisation again.
Its members included historic Bond villains Dr No and Ernst Stavro Blofeld, but the group disappeared from the films for decades due to a legal rights dispute that was only resolved two years ago.
Britain's Guardian and Telegraph newspapers gave SPECTRE the maximum rating of five stars, the latter praising the film's 'swaggering show of confidence'.
However, the Financial Times gave it only two stars and said the film was attempting to tinker with the winning formula of 2012's blockbuster Skyfall while 'clearly being thrown into panic at the thought'.
SPECTRE was filmed in Austria, Britain, Italy, Mexico and Morocco and includes the usual Bond ingredients - high-speed chase scenes, sultry female leads, exciting gadgets and witty one-liners.
"I came here to kill you," Bond tells new bad guy Franz Oberhauser, played by Christoph Waltz.
"And I thought you came here to die," Oberhauser counters.
"Well, it's all a matter of perspective," Bond replies with a smirk.
There have been doubts over Daniel Craig's future as the sixth actor to play Bond after he voiced unhappiness at the prospect of doing a fifth film -- despite being contracted to do so.
He told Time Out magazine he would rather 'slash my wrists' than play the famous spy again, adding, "If I did another Bond movie, it would only be for the money."
An online poll by Britain's Independent newspaper on who should play Bond in the next instalment of the franchise found that most respondents would pick Mr Craig, followed by British actor Tom Hardy, who recently starred in Mad Max: Fury Road.
Under Mr Craig, Bond has transformed from urbane and dandyish into a rugged and troubled intelligence professional, a change not all critics appreciate.
"Daniel Craig, as Bond, looks like a security guard, not a man who moves easily at the highest levels of society," Telegraph columnist Charles Moore wrote.
