E.T.
The Mind of Mr. Soames
The TV show Parenthood has a child character who is autistic and several plots revolve around him.
Abed on Community is one of my favorites.
The new show The Good Doctor has such a lead, but it has some issues that rate a very limited recommendation.
There’s a little bit of stuff in WarGames* with some quite realistic full-on computer nerds. Eddie Deezen in particular has some classic AS traits. Bonus: I’ve been in the building it was filmed in and knew people there just like them.
- Checking IMDb: Wait a second, Michael Madsen was in WarGames???
Probably the best example of a positive, realistic (for a sitcom) autistic character. Made by a show creator, Dan Harmon, who may be on the spectrum himself. Plenty of situations to discuss.
How old is your son? The goofier, more caricatural characters may be suitable for a young child but not good examples if your son is older.
Doctor Lazarus is Alan Rickman’s character, so not him. The Thermian aliens who abduct the actors would totally fit.
Rainman features an autistic character, but it doesn’t fit your criteria because Dustin Hoffman’s character isn’t high functioning enough to want to try to fit in or learn how to deal with neurotypical people. Tom Cruise learns how to accommodate his brother and not be such a jerk all the time, but Hoffman’s character doesn’t change in the movie.
While looking for something else, I stumbled across “Atypical” today. “Parents need to know that Atypical is a comedy about a teen with autism (Sam) who decides it’s time to find a girlfriend.” Sexual content.
(I use that site when I’m looking for dramas so I can limit the amount of gore I see.)
They also have a list of books with characters on the autism spectrum, which I’m linking just fyi: Books with Characters on the Autism Spectrum
Good one, but C3PO might be an even better choice in that vein.
If he likes Data, he might like Spock, too. Depending on his age and interest in reading, Issac Asimov’s Robot Series might be good.
Ben Affleck’s character in The Accountant. Picture John Wick, CPA - autistic forensic accountant/assassin.
By Grabthar’s Hammer…what a bargain.
Thank you all. These are all great. I’m also expanding to think of characters like Sherlock AKA the disconnected genius. He doesn’t necessarily get humanity, or see why he should bother, but has his filter, Watson, along to help him navigate the world.
Thank you for the link. I use this site when I’m researching video games. I had no idea they included this sort of information.
You got me. I just like saying “By Grabthar’s Hammer.” 
The recent movie reboot of Power Rangers was surprisingly likable and character-focused, and features Billy the Blue Ranger, a sensitive and positively portrayed autistic character who is integral to the team. Well worth a look.
The current tv show Scorpion is about a team of geniuses who have a hard time relating to people, the waitress who is specifically there to help them relate to people, and her autistic son who is also a genius.
The classic British show Red Dwarf (on since the 80s, now in its 12th series) is about three guys and an android lost in space and time. I am pretty sure it’s ok for kids.
Alphas Alphas (TV Series 2011–2012) - IMDb only 2 seasons but Gary was my favorite Alpha.
Bones Temperance “Bones” Brennan is never outright said to be on the spectrum but she displays a lot of the mannerisms. I'm an Autistic Woman, and Bones Is the Only Character Like Me on TV | Glamour
Give The Bicentennial Man a shot. Stars Robin Williams and about a robot who wants to be a human.
Really amazing story.
Robin Williams as Mork is another example. Every show was a life lesson smothered in slapstick.
I don’t know how old the OP’s son is, but he might enjoy Small Wonder, a sitcom about a robot girl who has no emotions in the early seasons. It was aimed at families with pre-teens. You can find both shows on YouTube.