I’ve always felt like in retrospect my preference as a 10YO for Mary Ann was based on the notion of ‘who would I have the better chance with?’ or ‘who would make me feel less inadequate’?
I think the fact that Tina Louise was resentful about playing the part came through on screen and put people off. There was always a touch of aloofness in her character that made her less attractive.
As for her not knowing she wasn’t the star, I remember on writeup about the shoe (before it aired) that implied Jim Backus was the star and the premise was his living like a millionaire (with the implication that he would be playing Gilligan). It may have been a misunderstanding by the reporter, or it could have been that Backus also had been led to believe he’d be the star (though he went with it, mainly because he already had an acting gig that season as Mr. Magoo and probably couldn’t managed the two roles). If Backus had been misled, it’s possible that Tina Louise was, too – though she was less gracious about it.
That would have been a lot more likely in the case of Jim Backus, since he had already been a fairly big name for quite a while. He was also the only member of the GI cast who was ever allowed to ad-lib, and he did it brilliantly.
Well remember, this was a time of ‘Day Players’. Where you’d have a small regular cast, and then Day Players who were not really under contract and weren’t payed very well. On Star Trek, one of the reasons Shatner treated the others so poorly was that only he and Nimoy (and maybe Kelly) were “Stars”, and the rest (Takei, Nichols, etc) were only Day Players.
I could be wrong, but I recall reading Shatner justifying himself that way.
So yeah, everyone was the star of GI, because they were all under contract.
Here is an a clip from the pilot episode, where Mary Ann is actually a typical scatter-brained blonde secretary, Ginger is a red-haired secretary, and the professor is actual a high school teacher.
Ginger is in that ball gown while Mary Ann goes around in tiny shorts and a half shirt with a bare midriff showing more skin then she isn’t. Yet somehow Mary Ann is considered the surprise choice. It’s really not that surprising.
She had the better personality, seemed happy and upbeat most of the time despite their circumstances and could make coconut cream pies. It’s not complicated.
I always thought Tina Louise must not be the sharpest knife in the drawer. If she thought she was going to be the focal point of a show called Gilligan’s Island (featuring Gilligan), about movie star stuck on island with civilians - how long could that show have gone on? It would have gotten pretty boring really fast. There’s just not that much to go on.