"This particular day is the best moment in my life. The whole day has been magical. The whole world is showing up for me and wishing me well on my 90th birthday, and I can't be more blessed than that," Bennett said.
Others in attendance included Steve Buscemi, Katie Couric, Regis Philbin, Gayle King, Christian Siriano and a gaggle of grandchildren.
Lady Gaga and Bennett have built a lasting friendship that began when they collaborated on a version of the song "The Lady Is a Tramp" and the album Cheek to Cheek.
"Well, we just love one another. We're both Italian-Americans and we understand one another. I love her family. I love everything about her and, you know, we just get along," Bennett said.
The birthday bash was held in the Rainbow Room at Rockefeller Plaza. Willis attended with his wife, Emma Heming, and the action star admitted he used to think making it to 90 was enough. Now, after seeing Bennett's youthful exuberance, he's not so sure.
"If you have to make a deal? I'll take 90 and that's it. Now, seeing this genius singer and great man at 90, it's like I want to ask him that question, but I'm too afraid to," Willis said.
Travolta recalled hearing Bennett's music from an early age. He grew up not too far away from Bennett in New Jersey and the singer's music "saturated our home."
"I was saying that Barbra Streisand and Tony Bennett are my bookends, my favorite singers. They're the soundtrack to my life. I don't know how it gets more special than an artist being a soundtrack for someone's life," Travolta said.
Musical performances from the event will be shown on the prime-time TV special, Tony Bennett Celebrates 90: The Best is Yet to Come. It airs Dec. 20 on NBC.
"I love life. I love being alive. I think it's a great gift to be alive, and I just cherish every moment that I'm alive," Bennett said.