All those guys you mentioned were creative and clever and thoughtful, so the vulgarity was just a part of the act. These guys say the F word and expect the laughs to rain down. Effing lazy of them.
George Carlin used to say things like "Ever wonder why you park in the driveway but you drive on the parkway?" Now that's clever and funny.
Eddie Murphy is a genius and he created characters that live on in our memories and still bring a smile.
Robin Williams was not vulgar, nor was Rodney Dangerfield.