Yes, Jimmy Kimmel was funnier on the Man Show, because it was a more crude type of humor that fit him really well. You could tell when Kimmel was on the Man Show, that he was just being himself. The jokes on his show on ABC have to be more mainstream, and it doesn't come as naturally to him. He is a funny guy, though.
Jimmy Kimmel's style of humor is not suited for the very safe, uncontroversial humor that is typical of late night shows. He is far too restrained in this show to be very funny. In The Man Show he was able to be much more offensive and unrestricted with his humor and therefore funnier.
I find it hard to tolerate any of the late night talk show hosts. For myself the only presenter who ever manages to consistently make me laugh is Conan O'Brian. Kimmel's strength is not in his joke telling, and I find his interviewing style to be poor. The name of the show might have changed, but the flaws have not.
Jimmy Kimmel was never funny. He is not funny at all. He should not be on television. He just thinks he is funny. He has a bad attitude and thinks he is a better person then he is. Take him off television for good. The Man Show was horribly disrespectful to women and he is a big jerk.