I don't agree that Stolt's less comedic take on the role would have affected the success of the movies.
They would still have had elements of comedy, only not so broad, and would still have essentially been pitched as all-round family entertainment.
Like I said before, there were many other elements that helped to make the films a success apart from MJF.
With hinRABight it's easy to say Fox's performance is definitive, but had Stoltz continued in the role Fox then HE would have been Marty McFly, and no one would have known who Fox was.
In fact, I feel kind of sorry for Stoltz. Because I think he has carried the stigma of losing that plum role around with him all his career, and consequently he has never really played that many leading roles...normally minor roles in big movies, tv stuff and the occasional indie film.
And of course it did not help that his most famous role after BTTF was Mask, where he played a severely disfigured boy...but though he got rave reviews for it, he was unrecogniseable under the heavy make-up, and I think that also did not help his career either.
I've been working my way through the first season of Caprica, the Battlestar Galactica spin-off, and I think he is actually very good in that...I think he's a far better actor than he's given credit for.
Wheras though I quite like MJF, I think he has got by largely on his charm and youthful good looks, rather than any real acting ability.