For me, like many people, Robin Williams was the crazy uncle of the family. Unlike many other actors and comedians, there was something about his presence that made him relatable, if off the wall. Perhaps part of it, for me, was because I started watching him play Mork while I was still rather young and impressionable. Through Mork, Robin played a naive, yet lovable, crazy person, someone who helped us examine the craziness in our own lives that we otherwise took for granted.
In a way, his characters in my two favorite movies of his, Good Morning Vietnam and Dead Poets Society (whose ending will make it so I might not watch it again), expanded on this identity that he created with Mork. In both, he is still an outside observer who helps people understand more about life through his wild manner. In both, he was also a bit naive and surprised by the harshness of reality.
His passing also brings to light the loneliness that so many people feel. It amazes me how much we, as humans, isolate ourselves even when we are surrounded by others. In his case, perhaps his talent and energy brought about a bit of a curse for him. Perhaps he felt like an outsider in reality which is why some of his roles were so convincing.
I'm not going to pull a moral out of this. He was a great man who will be missed.