In a lot of ways, his defining role was the adult Peter Pan in Hook. I always loved this movie. Rewatching it today had the effect of helping me realize something important not just about the movie, but J.M. Barrie's creation in general, that lost little boys and pirates are very much the same except: the ability to embrace happiness and family (which may be one and the same). You may or may not know how Williams struggled in recent years with a divorce that gutted the financial legacy of a career that was sadly in decline. He was a man who embodied joy in his best moments, but knew pain as well as any clown. In the end, it seems his demons won out. He is not a cautionary tale, though, but a model we can only hope to improve upon. Hence Peter Pan. Hence learning what he tried to teach, to live. The little boy who didn't want to grow up, and succeeded in that aim for an awfully long time.
I haven't seen all of Williams' films. I haven't seen Good Morning, Vietnam, haven't seen The Birdcage. I loved everything I ever saw him in, though. I loved Dead Poets Society (who doesn't?). I loved Awakenings. I loved The Fisher King. I loved Aladdin. I loved Mrs. Doubtfire. I loved Flubber. I loved Good Will Hunting. I loved Patch Adams. I loved Bicentennial Man. I loved Insomnia. I loved One Hour Photo. I loved Happy Feet. I loved License to Wed. His cameos in The Adventures of Baron Munchausen and A.I. Artificial Intelligence were crucial additions to brilliant films. What Dreams May Come will perhaps one day be discovered for the great work of art it is.