The 58-year-old actor - who played the superhero in Lois + Clark: The New Adventures of Superman from 1993 to 1997 - admitted he has reservations about the filmmaker's new movie, which stars David Corenswet, and his vision for the character.
He told TMZ: "How woke is Hollywood going to make this character? How much is Disney going to change their Snow White? Why are they going to change these characters to exist for the times?"
Gunn had previously compared his movie to "the story of America", with a central character who is "an immigrant that came from other places and populated the country."
Referencing the traditional Superman motto of "Truth, justice, and the American way" - which has evolved over the years and has most recently been "Truth, justice, and a better tomorrow", Cain said: "We know Superman is an immigrant — he's a freaking alien.
"The 'American way' is immigrant friendly, tremendously immigrant friendly. But there are rules.
"You can't come in saying, 'I want to get rid of all the rules in America, because I want it to be more like Somalia.' Well that doesn't work, because you had to leave Somalia to come here. There have to be limits, because we cant have everybody in the United States. We can't have everybody, society will fail. So there have to be limits."
Cain's comments came after Gunn described Superman - which also stars Rachel Brosnahan as Lois Lane and Nicholas Hoult as Lex Luthor - as a tale of "basic human kindness".
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