Which call of duty games are good on PC?

I have a windows PC and I know that COD 2 and 4 work well on PC and almost as well as on console. The question is, however, how well do World at War, Modern Warfare 2, and Black Ops work on PC? Are they too buggy? Are they worth paying the money for now? Ever? Should I wait until they get cheaper before I invest in a game that is only okay?