I actually made this point once while working for Apple, saying it was like thinking about whether the other side had won World War II.

But I think the point still stands that Microsoft has managed to cause far more harm during their reign than Apple, precisely because they have been more successful. I also think that Apple is somewhat constrained in the damage they can do, because Steve Jobs wants to be a Tyrant of Taste, more so than Ruler of All He Surveys. He has little interest, for example, in the mass business market or the clunky boxes at the bottom of the market. To have Apple branded boxes at that price range, with all the compromises that entails, seems to horrify Jobs.

As for other product areas, probably the most tyrannical is iTunes. But even there, the damage is constrained by the fact that the majority of people still just pirate their music, anyway.