In my opinion, biographical films should try to portray the character and events as realistically as possible. This is particularly important, as biographical movies have a far wider audience than books and other biographical material - and also to preserve the accuracy of the character and achievements; not only of the main subject but also of the characters around the subject. In all of these respects, by all accounts, The Imitation Game, is a failure in the portrayal of Alan Turing and his fellow cryptographers.
The movie gets too many things wrong. Alan Turing was not a self centred, isolated genius who single handedly broke the Enigma code. The Enigma code was not the only code to be broken, and its success did not happen all at once. Fellow cryptographers also had significant contributions to the project. The military management did not actively hinder the project. And so, the list goes on.
That said, the performance of Benedict Cumberbatch was impressive - and the movie does make a fine inspirational tale. It's just a pity that the real tale is just as amazing and didn't need to be fictionalised.