Yeah but he always comes out ahead in his own comic book where he can't lose, so chances are his villains are significantly less threatening than other super-heroes. If you even the playing field and put batman up against say superman, I don't see him kicking that much ass.
Well, that's true of every superhero in their own book, but all of them lose there sometimes too.
Ever read "The Dark Knight Returns"? A 45 year old Batman comes out of retirement and starts cleaning up Gotham City. By the end, all the thugs in town are worshiping him, and he fights Superman to a draw before faking his own death and escaping. I'm not worried about him holding his own.