Maybe it’s just a selective effect: some actors like, or don’t mind, science fiction roles, and once they’ve been in a well-known SF role directors and casting agents think of them when another role opens. But it seems like some actors who had previously been known for other genres get trapped in a SF “ghetto”. Is this real? The following come to mind:
-Roddy McDowall
-Ernest Borgnine
-Charlton Heston
Others?
I don’t think Charlton Heston or Ernest Borgnine, despite many appearances in SF, were ever typecast as “SF actors”.
Neither was James Caan, despite lots of SF films (Countdown, Alien Nation, Rollerball, The Lathe of Heaven)
Even Roddy McDowall is a stretch.
He’s been in a ton of stuff. I’m not even sure what small fraction of his body of work is in SF. Even after the Apes movies/TV series, he made a ton of TV and movie appearances across several genres.
I think the first role people think of when they think of Heston is Ben Hur. Yeah, folks’ll also remember Planet of the Apes and Soylent Green, but for those, I think they’re mostly just remembering his delivery of the climactic lines.
In all fairness to the OP, Ben Hur was years before Planet and Soylent. It’s possible to argue he was ghetto-ized after those.
But if he were actually ghetoized, then that wouldn’t be the first role we thought of any more.