The reviews for Kick-Ass were impressive with one comparing it to Airplane. Basically, the material that I saw made the movie sound extremely funny.
Unfortunately, the potentially funny bits were flawed either with excessive realism or serious narration. For instance, the over-the-top combat skills of Hit Girl could have been funny without the overly realistic portrayals of bloody violence. Comic book violence (less bloody) would have done the trick and allowed the absurdity of her kicking the crap out of a room full of people to be funny.
I'm not saying the movie was horrible but I am saying that it was just plain average.