I dunno. I mean, he feels more of a real kid than Elmo, but I don't think he has that "hook" to differentiate him as anything more than a young male monster; I guess maybe the whole "step brother" thing, but he has to be more than that.
And lest we forget, characters come and go. Rudy may wind up facing the same fates as Lulu, Curly Bear, Juliet, Betty Lou, Farley, etc.