Forget about some of the shitty movies the man has done. Watch his stand-up and tell me he is not hilarious. Robin Williams uses his energy and ability to do funny voices to keep you laughing the entire show. My brother told me to watch his Live on Broadway special on HBO and I thought that it would be pretty stupid. I could not have been more wrong.
It would be unfair of me to say that all of his movies were shitty. If you want to laugh, watch his opening broadcast in Good Morning Vietnam and tell me you do not crack up. Or any of his stuff in Aladdin.