The Apple fanboys at Engadget would tend to disagree with you. They claim Windows Media Center is the best on the market. I agree. Apple TV is a joke.This will likely not be a popular topic, but Microsoft has been on the PC home theater bandwagon for some time via Windows Media Center. (thus far they have done poorly in my opinion)
"Once you switch to Windows 7 Media Center there is no going back. It might not seem like that much at first, but when you try to go back to Vista or even another solution like Moxi or TiVo, it is like going back in time. The fact is that Microsoft has been in a league of its own with Vista Media Center and while the competition is still sitting idle suing each other, Microsoft has yet again raised the bar. There is no doubt in our mind that it is the all around best DVR solution available today..."
http://hd.engadget.com/2009/07/27/windows-7-media-center-review/