The actor made the claim at the opening of the Roybal Film and Television Production Magnet - a new school in LA for underrepresented students wanting to get into film and television.
He joked: "When you think of me you just think he's just the best Batman."
Fellow star Don Cheadle, who was also at the event, quipped that his pal was only the "best available".
Clooney then further amused the delighted audience by saying of Affleck in the role of Batman: “He’s got nothing on me.”
And George Clooney knows his audience so he even throws in a Batman reference. “When you think of me, you think he’s just the best Batman,” to which Don Cheadle quips, “best available.” Then Clooney brings up Ben Affleck as Batman — “He’s got nothing on me.” Crowd loved it. pic.twitter.com/ntO4gLxc8X
— Chris Gardner (@chrissgardner) September 14, 2022
The father-of-two may not have been serious as he has previously stated that he “f**ked up” the role.
Clooney,61, had starred as the superhero in 1997's Batman & Robin, which is widely considered by critics and fans s as one of the worst superhero movies of all time.
The star donned the cape when Val Kilmer didn't reprise his role after Batman Forever.
Affleck has appeared as Batman several times starting with Batman v Superman: Dawn of Justice before a cameo role in 2016's Suicide Squad.
He then had a leading part in Justice League and will make another appearance in the DC universe in next year's Aquaman sequel.
Actor Adam West, who portrayed Batman in the 1960s ABC series Batman Returns and its 1966 theatrical feature film, for many, has been considered the best.
The most recent is Robert Pattinson in The Batman, released in March.
The British actor, who starred alongside Zoe Kravitz, has had mostly favourable reviews.