Let's not forget - Chris Rock was THE man when it came to stand-up in the late 90s to early 00's. He was hosting awards left and right, he wasn't always brilliant, but his jokes and sarcasm were dope. Chappelle made his breakthrough with his show, not stand-up, before that maybe people knew him as the comedian in Nutty Professor and Half-Baked. Chappelle's show is what made him a real comedy star.
If we're talking stand-up, then I'd take Chris Rock over Chappelle. Not that Chappelle is not funny, but Rock was funnier in his prime.