Robin Williams is strange. It seemed like he was going years without being funny, just doing crappy movies and doing unfunny appearances, then I saw him on "In the Actors Studio" (or whatever that stuffy actor interview show is called) late last year, and he was HILARIOUS. Had me, my mom & my dad in physical pain from laughing. He was all over the map (as usual), but it worked again.
George Carlin seems to go in cycles: plain funny, wierd but still sorta funny, crappy/deranged, back again. I like how he will go off on literally ANYONE and ANYTHING on Earth. During one routine, just as I was getting annoyed that he sounding like a doctrinaire liberal, he went and declared atomic war on feminists. :shock:
Sam Kinnison was funny as hell, vulgar and awful sure, but he used it as a tool to amplify his humor, rather than as a substitute for humor, if that makes any sense.
Haven't kept up with Chris Rock, which is a little wierd since I liked the stuff I saw when I saw it.