Greeted with a standing ovation, the US director -- whose works from "E.T" to "Indiana Jones" are the focus of a retrospective at Paris' Cinematheque film centre -- told the room in French, hand on his heart: "Je t'aime!"
"I'm a storyteller," the 65-year-old told the filmmaking masterclass between screenings of his new film "War Horse". "For a long time movies were everything in my life -- and if I don't have a story to tell I go crazy."
"Ask my wife and my kids what's it's like to have me without a movie in my immediate future to direct!" he quipped. "I'm a terrible person to live with!"
"I mope, I walk around the house in a terrible state, I'm miserable!" Spielberg joked. "So my family is the first to call my company and say 'Is there anything in the files he can direct? Please help us!'"
Revealed to film buffs with the 1971 car chase thriller "Duel", then to the mainstream with "Jaws" in 1975, Spielberg has shot more than 30 feature films as well as a string of productions for television, from episodes of "Columbo" to the hit series "Band of Brothers" in 2001
"I got starting making movies as a kid because I couldn't think of anything more fun to do," Spielberg recalled. "When I was 13 there was absolutely nothing that interested me more than to take a movie camera and tell a three, four minute story."
"And when I make a movie today, I get that same energy, the same excitement," he said. "I remember the same feeling at 12, 13 years old, as the feeling I still had as I turned 65. That has never gone away."
The director has been something of a work horse of late, directing the 3D blockbuster "Adventures of Tintin: Secret of the Unicorn", which hit screens in late 2011, before launching straight into "War Horse".
When in the grip of a story -- as was the case for "War Horse" which he based on a children's book by British writer Michael Morpurgo, and a play adaptation by Nick Stafford -- Spielberg works non-stop.
"From the time we started working on the script, to the time I called action for the first time in Devon (in southwestern England), was seven months," he said, "which as you know is a very, very short time."
"That's an 'E.T.' sort of record, since 'E.T.' took seven months from the time the script was written to the time we shot."
"War Horse" tells the story of Joey, a horse raised in the bucolic English countryside who is torn away from his home -- and stable lad Albert -- and sent to France to the battlefields of World War I.
Almost deliberately old-fashioned, the movie pits noble beast against the horrors of war with sweeping, emotional set pieces that earned it a Golden Globe nomination for best dramatic film, but has divided critics.
"I cried when I saw it on stage," Spielberg said of the work. "It's a straight narrative story. It's completely clear: I like stories that are not encumbered by excessive symbolism or metaphor."
Asked by the event host, the filmmaker Costa Gavras, to offer a tip to the aspiring filmmakers packing the audience, Spielberg said casting was key.
"First of all, the best thing you can do is to cast the right actor. If not, you have to work ten times more later.
"Once you have casted, listen to the people you casted: what do they have to bring? Let them do their work, read the books," he said. "Why cast talented people if you do not listen to them? You got to listen more than you speak."
Spielberg said the best piece of advice he received as a young filmmaker was from the French New Wave director Francois Truffaut, who he got to know in the 1970s.
"He came to Mobile, Alabama, he had just finished 'Small Change' and he said: 'You must work with kids,'" Spielberg recalled.
"What you are is going to be relevant in your movies," he said, when asked to pin down the secret of his success. "This is just who I am."
"I even never drifted away from that kid -- and maybe here is my secret: childhood, to be like a child."