It's funny that Leary & Hicks were mentioned side-by-side, seeing as the former stole the latter's act every bit as blatantly as Mencia's thefts have been.
Unless you mean "yelling the punchlines instead of just saying them", I don't see how Leary made any of it "his own". He just retold another person's jokes (sometimes in the same words) and pretended that they were his own.
Yeah, I would hate Leary, since he's basically 90% Bill Hicks... but he has the asshole song, and Rescue Me... and is a decent actor... so yeah.
I do notice though for most of the people who steal a joke... they don't do anything differently but yell it. Dane Cook, Carlos Mencia, Dennis Leary... it's just weird. Like the time Mencia ripped one of Cosby's best bits about how fathers usually don't get any respect compared to mothers. Mencia took it word for word.... except he just yelled and added a "MOTHERFUCKER!!!" or two.