there was an identical thread about this topic not too long back and then the article about the pitch that was swung and missed the most.
theres SO many different variables that need to be taken into consideration for a discussion like this. Johan's changeup is only as good as it is because of his fastball. Brad Lidge's slider is only as good because of his fastball, etc...If you take a pitch from someone arsenal and put it in someone else's it will have a completely different effect and result, so in all reality, this discussion is all moot. except for cole hamels of course.
George Bush claimed that the federal government was monitoring Cole Hamels actions because, "Any man with a change-up that deceptive must be monitored for national security reasons." In actuality, Bush is afraid Hamels may attempt to have sex with his twin daughters. He already has, twice.