I've never ever understood why Robin Williams is supposed to be funny. Just looking at the guy depresses me; always has, way back on Mork & Mindy, long before I had any idea what his political leanings were. The only thing I've ever seen him funny in is Mrs. Doubtfire, and that was still depressing.
MM
I did like him in Good Morning Vietnam but he got a bit gooney...
I don't think Robin Williams is that funny, but I can sort of understand why others do. But Adam Sandler - there's a guy whose success totally mystifies me.
Then do NOT rent the movie The World According to Garp. That will certainly put you right over the edge.