Random musings:
I'm not sure that there is a particularly clear definition of a "proper" biopic. Fortunately, they don't have to follow the model of a written biography (the first 50 pages or so devoted to the history of the subject's parents, grandparents, etc..). Curiously, many prose biographies (especially those aimed at a popular audience) have adopted what I call the "Kane model", beginning with a funeral, or some event near the end of the subject's life as a foreshadowing of what is to come.... Surely 'Kane' wasn't the first narrative to do this.
Because biopics must often deal with historical material in a shorthand way, there's frequently an element of campiness to the way they zoom through various cultural reference points.. Russell had fun with this kind of name-dropping in an early scene in 'Lisztomania' (in which Levi Strauss is confused with Levi-Strauss), and it's also probably part of the appeal of Oliver Stone's 'The Doors".
Another curious aspect of biopics is the way they occasionally feel forced to end with a happy ending even when the facts deny one. I'm thinking of films like 'Tucker', though perhaps 'Ed Wood' and "Man on the Moon' count as well. My favorite such moment is the ending of 'Great Balls of Fire', which ends somewhere around 1960 with Jerry Lee Lewis' career faltering and his personal life shattered, but assures us that he's 'still rocking'.....
Robert Hunt