Sure, he's best known for his zany antics and stream-of-consciousness comedic improvs, but Robin Williams was also comedic actor with soul.
He often chose movie roles that were beyond simply "funny." His characters had humor, warmth and heart. And for every Robots, or Patch Adams, there was a Birdcage.
Robin Williams made movies that didn't glorify violence or traffic in despair. His movies were the opposite, he glorified hope in the face of great obstacles. Which makes his death by his own hand even more confusing.
Clearly he struggled greatly, as we all do, money and fame do not soothe a tormented soul, but he was able to express his hope through his roles, even if the struggle proved too much for him personally.
So if you are going to delve into the Robin Williams oeuvre, here is the definitive collection of the top five must see Robin Williams movies ever made that aren't Good Will Hunting or Dead Poets Society.