If not for Star Trek, I say William Shatner would still have gotten lead roles in other shows. More than one, as he did with The Barbary Coast, TJ Hooker, and so on. He would still have become a nationally famous star. Not everybody's got it, but he really had it, whatever "it" is.
My guess is that Leonard Nimoy would have been a visible supporting actor and steadily-working voice actor. Without his cult following from Star Trek, I think he would have been seen as too "exotic" or something to get leads. Even after ST, his role on Mission: Impossible was of the ensemble variety. I don't suppose his poetry and photography books, and autobiographies, had a real audience beyond Spock fans, his pre-sold audience. And I doubt he would have directed any major motion pictures if not for his Spock-induced leverage over Paramount, which got him started on that.
The whole cast deserves discussion. One actor, whom I'll call Walter K (not his real name) seems to have been of two minds over the years. Sometimes he'd say that ST typecasting cost him all kinds of roles, and other times (I think later on) he would admit that, were it not for ST, he might have simply been an unemployed actor altogether, instead of getting supporting roles in the ST movies. Could he have been the next Dustin Hoffman, if only there were no Star Trek?
My guess is that Leonard Nimoy would have been a visible supporting actor and steadily-working voice actor. Without his cult following from Star Trek, I think he would have been seen as too "exotic" or something to get leads. Even after ST, his role on Mission: Impossible was of the ensemble variety. I don't suppose his poetry and photography books, and autobiographies, had a real audience beyond Spock fans, his pre-sold audience. And I doubt he would have directed any major motion pictures if not for his Spock-induced leverage over Paramount, which got him started on that.
The whole cast deserves discussion. One actor, whom I'll call Walter K (not his real name) seems to have been of two minds over the years. Sometimes he'd say that ST typecasting cost him all kinds of roles, and other times (I think later on) he would admit that, were it not for ST, he might have simply been an unemployed actor altogether, instead of getting supporting roles in the ST movies. Could he have been the next Dustin Hoffman, if only there were no Star Trek?