The occasion was a tribute held in the director's honour Thursday evening in Los Angeles, at which he was presented with the American Film Institute's lifetime-achievement award.
Among the guests were past collaborators like Steven Spielberg and Harrison Ford, as well as his former mentor, Francis Ford Coppola.
The admission came during an acceptance speech in which Lucas tipped his hat to Coppola for helping him develop his skills as a screenwriter.
George Lucas poses with his AFI award. (AP photo)
"He took me from not being able to write a word in terms of writing screenplays to being the king of wooden dialogue," Lucas said.
Although the Star Wars movies have earned billions of dollars at the box office (the latest, Revenge of the Sith, is on track to gross at least $400 million US), critics have repeatedly taken Lucas to task for the way his characters speak.
Roger Ebert, for instance, wrote in his review of Sith that "The characters talk in what sounds like Basic English, without color, wit or verbal delight, as if they were channeling Berlitz."
A younger Lucas directs Anthony Daniels, who played C-3PO, while making the original 'Star Wars.' (AP Photo)
Even devoted fans have been disappointed with lines like "Hold me like you did by the lake on Naboo...so long ago...when there was nothing but our love...no politics, no plotting, no war," which is delivered by Natalie Portman's Padmé Amidala in a love scene with Anakin Skywalker (Hayden Christensen).
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Indeed, the actors who appear in his films have also told Lucas they don't like his screenplays.
While filming the first Star Wars movie in 1977, Ford famously said of the script: "You can write this [excrement], George, but you sure can't say it."
Lucas' moment of self-mockery matched the tone of the tribute, which strayed into roast territory at some points.
Mark Hamill and Carrie Fisher – who played Luke Skywalker and Princess Leia – joked about the avalanche of merchandise that followed the success of the original Star Wars movie, describing how their characters were turned into Pez dispensers, shampoo bottles and electric toothbrushes.
"People are still asking me if I knew it was going to be that big of a hit," Fisher said. "Yes, we all knew. The only one who didn't know was George."
Robert Duvall also appeared, discussing how Lucas made him shave his head for THX 1138, Lucas' first film.
Spielberg presented the award to his friend, hailing him as a populist science-fiction pioneer in the same mold as H.G. Wells and Jules Verne.
"You have many years ahead of you to create the dreams that we can't even imagine dreaming," Spielberg said. "You have done more for the collective unconscious of this planet than you will ever know."
Also on hand was William Shatner, who performed a reworked version of the Frank Sinatra song My Way to describe Lucas' career. The Star Trek actor was accompanied by a chorus line of dancers in white stormtrooper costumes.
"Live long. You've already prospered enough," Shatner told the guest of honour.
After poking fun at his shortcomings as a writer, Lucas said he was humbled by the accolade. "I'm also extremely grateful that I discovered my passion. I love movies," he said. "I love to watch them, I love to make them."
