Though not a movie character, I'd say Ford Prefect from HHG2TG (there was a TV mini series at some point, the movie is horrible, but the TV series is a lot of fun). Though he's an alien, he's kinda like us. Doesn't understand sarcasm, doesn't understand why earthlings always have to state the obvious, doesn't 'get' human emotions. I'd suppose his love for alcohol borders on the obsessive too .
Sheldon, he's 'a bit' exaggerated, but he really has a lot of aspie traits.
Agent Smith (this is a joke, LOL), but his skepsis and misunderstanding of human nature are typical. He also greatly fails in understanding his own actions (thinks he's so logical while really...). His communication skills are kinda aspie, very one-sided, only believes in his own opinion. I know he's a programme, but he shares some aspie traits, too.
All the aliens from 3rd Rock from the Sun, because, really, you understand why...
The professor from Back to the Future, and that kid as well (forgot his name)
Stitch, LOL, super intelligent, but can't talk. Throws anger attack on a regular basis.
Probably know many more, but no time right now...