Gibson was shunned from the industry following antisemitic and racist remarks he made.
However, his career somewhat recovered with Hacksaw Ridge, in 2016, for which he got a Best Director Oscar nomination.
He also had the financially successful Christmas comedy Daddy's Home 2.
"Mel Gibson came back. Not to the exact extent he used to, but he's come back," Engelmayer said, before adding that Depp is viewed as "more charming and more delightful."
The Pirates of the Caribbean star's legal issues are also a civil matter and not a criminal one.
"He'll be cast in independent films or films where he is maybe the bad guy, a criminal, a mobster. Someone who at first is not a likable guy, not a fun guy, but someone who's the bad guy."
He had previously used the legal process in 2020 as he sued a British tabloid for calling him a "wife beater" but lost.
But in Fairfax County Court in Virginia, Depp and his lawyers are spending weeks in front of the cameras making the argument that Heard was the real abuser in the relationship and that she can't be trusted when she claims otherwise.
"Johnny Depp is showing studios and showing publicists that he can win audiences over," Engelmayer said. "That's the turning point of whether or not it's going to turn on Johnny Depp. This is not a criminal trial; it's a civil trial."
Engelmayer further noted that despite the relationship between Depp and Heard appearing to be "difficult, psychologically and emotionally troubled people," the Aquaman actress' career is expected to be fine.
"She comes out as a woman who is speaking out and speaking her truth." She'll be picked for movies too. And the box office will judge both of them on that," he continued.
Depp accused Heard of defaming him in a December 2018Washington Post op-ed titled: "I spoke up against sexual violence — and faced our culture's wrath. That has to change."
Heard has countersued and alleged Depp assaulted her numerous times before and during their marriage, which ended in 2016.