True but one could argue that the two are separate abilities. Madrox has the X-Gene and his dup's are clones made of his physical mass, also its something he had from birth, while Naruto's shadow clones are made up of shadows and are Ninja related, whereas Shadow Clones are a tech that needs to be learned. Ninja tech and X-Gene abilities aren't the same thing. Madrox could solve quatum physics given time, he can separate himself from his dup's for extremely long durations and far distances, Messiah Complex has his dup going to the future to see all the crazy stuff that went down and to report back about it.
I agree that the story does take a down turn by having so many copies and that having copies of oneself has been done to death, but unlike Naruto's clones Madrox' dup's have the odd tendency to act out in ways that he wouldn't, aborations to his psychy from spliting or darker aspects of him coming to the surface. Hell one of his dup's nearly kills a guy in a coma and another makes him "dopple" with his hand in a guys mouth, thus by making him explode. He later comes out saying somethings wrong with him cuz thats not how he would act.
I more interested with how he deals with having all the experiences that aren't his own, in my opinion, and why the aforementioned aboration plays out.