it's def not an easy choice.
personally for me... might have to go with Eddie Murphy. ONLY because his stand up career didn't last that long. And the other 3 have just as good material as stand-ups.
That's only if I'm comparing them as stand-up comedians though.
If I take movies into consideration then it's Chappelle. if I include movies & tv, then it gets more difficult. could be Rock, despite the fact how funny Chris Rock show was & how good he was on SNL.
edit. didn't watch the video yet but judging by the title they're just comparing who's the funniest though.... I mean then it's impossible. And if we're just going by "who's the funniest" then I'm gonna have to throw Patrice O'Neal's name out there. I mean obviously he didn't accomplish 1/10th of what the others did but just being funny? I'm not sure if there has ever been anyone like him.