The common wisdom has always been "write what you know." Yet readers often complain when some authors take it literally – when main characters are writers facing mid-life crises or other problems. In literature, no one is more guilty of this than Stephen King, whose worst works (books he's even since decried) feature alcoholic writers – which, throughout the 80s, he was. King claims he was so hooked on narcotics, legal and otherwise, he has no recollection of writing Cujo.
In film, author characters are often easier to get away with, as their actual work rarely needs to be heard nor seen, merely their presumed success or failure.
A "writer" is a common non-job for characters in a movie – much like an architect or marketing executive. They serve as an excuse for a character to own a house and live a life, but have little impact on the plot. However, they can serve as the very crux of the story - films about frustration or lack of drive or unexcised ambition and potential. Here are some of the very best.
Kenny Hedges is carbon-based.
So I suppose a simple top 5 in no order will do: Halloween, Crimes and Misdemeanors, L.A. Confidential, Billy Liar, Blow Out
He has his own website - thefilmreal.com - and is always looking for new writers with differing views to broaden the discussion.