Didn't Saving Private Ryan get rave reviews and maybe even win an award or two? Hey, personally, it's not my type of movie either, but one can dislike a movie while recognizing its value. On the other hand, one can like a movie while realizing it's terrible. I like those old kung foo movies, but I know they're not good.
But there's a fine line between irony and stupidity, and most of those parodies cross it. I'm not talking about flicks like Airplane! or The Naked Gun, I mean the ones that make fun of other, usually much better movies.