Comedians for me are hard to judge (stand up comedians) because they all seem to have a few routines that are very immoral, and that immediatly seems to turn me off. I guess Jerry Seinfeld is the only one I can think of that has a clean slate. haven't heard too much stand up, so don't jump down my throat, please.
As far as movies-
Bill Murray is probably my favorite. Ghost Busters, Groundhog Day, What About Bob? I can't believe no one's mentioned him yet. Others not mentioned that are good:
Bill Cosby, Robin Wiliams, John Candy, John Goodman, Tim Allen.
What about teams? Ghostbusters is pretty good. My favorite comedy movie is probably City SLicker II (yes, II), so i guess i'd say that those three guys do pretty good together. But hands down, the best performance, period (a duo)-
David Spade and Chris farley, "Tommy Boy".