Then came Sept. 11, and with it an urgent desire to help revitalize lower Manhattan.
The result: the inaugural Tribeca Film Festival, running Wednesday through Sunday with some 100 screenings, including the premiere of the new "Star Wars" movie.
"We talked about doing it for years, but we never made a plan to do it. There was always, 'That's a good idea, let's think about it tomorrow,'" Rosenthal said.
"It wasn't until after Sept. 11, when our neighborhood was so devastated, that we felt we wanted to do something to help our community heal, and to give our community something to look forward to."
And there's a lot to look forward to; for a first-time film festival, TriBeCa has drawn some big movies and big stars.
"Star Wars: Episode II — Attack of the Clones" screens on Sunday, four days before its nationwide release, as a fund-raiser for underprivileged kids and children affected by the terrorist attacks.
The opening night film is the premiere of "About a Boy," starring Hugh Grant and Toni Collette. Also on the schedule are premieres of "Insomnia," with Al Pacino and Hilary Swank, and "Divine Secrets of the Ya-Ya Sisterhood," starring Ashley Judd and Sandra Bullock.
A rock and comedy concert is planned for Friday night featuring Sheryl Crow, Counting Crows, Robin Williams and Jimmy Fallon.
Martin Scorsese is showing a series of restored classics as well as a selection of his favorite New York films, including "Manhattan" and "On the Waterfront."
And Kevin Spacey, Barry Levinson and Meryl Streep are among the jurors judging films in competition, all of which are from first-time filmmakers.
Writer-director Eric Eason thinks such a high-profile venue is the perfect place to show "Manito," his first feature. Shot and set in Manhattan's Washington Heights neighborhood with unknown, local actors, the movie follows two brothers trying to escape a family cycle of drugs and violence.
"We're still in the process of trying to secure distribution of this film," said Eason, whose movie won a special jury prize at Sundance for its cast.
Besides encouraging new filmmakers, the festival aims primarily to boost the economy of TriBeCa, the slice of downtown named for the Triangle Below Canal. An estimated 100,000 of the 370,000 jobs downtown are gone, and 11,000 businesses have closed or moved.
De Niro, who founded his Tribeca Productions film company there with Rosenthal in 1988, said he hopes "that a lot of people go, that it's successful, that it becomes a part of the New York cultural scene downtown."
"Things are slowly coming back, it seems to me. The quicker the better," said the 58-year-old actor, speaking from the New York set of "Analyze That," the sequel to the 1999 hit "Analyze This."
But some merchants' hopes aren't so high. The farther south you walk in TriBeCa — and the closer you get to ground zero — the streets grow quieter and the foot traffic thins.
"How is the festival going to help us?" asked Tirlochan Gil, owner of a souvenir and electronics store on Greenwich Street just a few blocks from where the World Trade Center stood. "Tourists don't spend money. They take pictures and go away."
Brendan Sexton, manager of nearby Brady's Tavern, said he hadn't heard much about the film festival. "Hopefully we'll get some overflow or something," he said.
But Lee McElfresh, a bartender at Puffy's Tavern down the street from De Niro's headquarters, was far more optimistic.
"I think it's very positive for the neighborhood," McElfresh said while sitting at the bar where a scene from "Changing Lanes," starring Ben Affleck and Samuel L. Jackson, was filmed. "I think they've done a fantastic job with banners and schedules and leaflets."