Probably would pay to see Chappelle, hard to say. I watch Bill Maher whenever he has an HBO special. Lewis Black, the same.
I won't consider the dead comedians or most of the old-stand by's. Like Seinfeld, last time I saw him perform (HBO?) he was brutally unfunny. And Jon Stewart doesn't do it anymore AFAIK but he was a funny bastard. If you asked me the funniest stand up I ever saw, I might pick his HBO special from about 10 years ago (before he was on the Daily Show). And Carlin was great, although I would say less funny than witty.
some I like that are still 'active':
David Cross (has he done any stand up in years? When he's on fire. He's probably my fav.)
Dave Attell (god damn funny, every time. He's a drunk, I can sympathize.)
Patton Oswalt (funny geek comedy, probably not for everyone)
Brian Regan (clean and bordering on banal observation comedy but funny)
Jim Gaffigan (funny but if you've seen him once, you've more or less seen his act)
Kat Williams (sort of 'one note' foulmoth but I laugh)
Demitri Martin (prop comedian essentially but he's clever)
Gervais and Izzard (had to have a couple of UK picks)
There is the red haired dude from those Vh1 shows who is pretty funny as well.
Fitzpatrick? Some Irish name.