Not so fast, ipodman – I believe the story is at least possible. For those who don't know the story, essentially Mary Magdalen had a baby by Jesus, born after he was executed. Mother and daughter escaped to France. They were able to enter noble society, and the daughter (presumably very dark or black, unique for France at the time) grew up and interbred with royalty. The royals' name was St. Clair, later anglosized to 'Sinclair.' (Presumably anyone with the last name of Sinclair is indirectly related to Jesus.) Through history, one person (the head of a secret priary) at a time was allowed to know of this secret, one of them being DaVinci. In an attempt to make sure the secret was not lost, he ingeniously left clues in his works. Wild enough to possibly be true!
My favorite is ‘Seabiscuit.’ It's actually quite accurate, Hollywood dramatics and structure requirements aside, and stays relatively true to the book. But the book is so much more indulgent (in a good way) and really tugs at the heartstrings. Highly recommended!
Interesting question! My answer would be a 'what if' style movie, such as 'what if Lincoln were not assasinated. How would history be different?' I'm working on a screenplay now that asks a big 'what if' question. I'll keep you all posted and let you know what it is once the wheels are set in motion (financing, stars committed, distribution deal, etc.).