Technically, we'd call it Autistic Spectrum Disorder, because when people think "autism" they are considering a much more extreme, unable-to-function issue, and to say ASD would be to include Asperger's Syndrome and other issues as well. No one is diagnosed with "Autism" anymore. This is why Mr. Chance and Howard Hughes might not be classically "autistic", they are certainly on the spectrum.
I was mentioning about Fantastic Beasts that I loved the main protagonist partly because he was autistic and he is functional. It was like watching one of my kids a number of years down the road, and my kids loved the movie because the portrayal was so recognizable. It's easy to make a character sympathetic because they have some clear deficiencies, but I think Fantastic Beasts does a great job of showing an autistic character who is interesting and watchable. I think that most people think of him as dull because they don't recognize that he is on the spectrum. However, Fantastic Beasts is far from a movie about autism. That is incidental. There are some great performances and stories that have autism front and center.
1. Lars and the Real Girl
2. Being There
3. Temple Grandin
4, Sling Blade
3. Punch-Drunk Love
HM: My Name is Khan, Guardians of the Galaxy (Draxx is on the spectrum), The Imitation Game, and, yes, Rainman.
I'm looking forward to Life, Animated.
A note on the TV series Parenthood, which has a kid with Asperger's Syndrome. The portrayal is amazing good, but the overly dramatic "tragedy" of parents having a child diagnosed with this is disgusting.