One of my all time favorite games is called Machinarium. Not only is it entertaining to play, but it is beautifully illustrated and animated and so of course the website reflects that. I think one of the reasons the website is so appealing is that the home page is exactly like the game’s home screen, and a demo can be played right from there as if you were already starting the game. Links to things such as FAQ, About, Store, and Wallpapers bring up a transparent screen where the content is displayed without ever leaving the actual home page where all the animation is going on. My absolute favorite thing about this website is how interactive the title is when the cursor rolls over. The speed with which you roll over actually determines the way the letters react, kind of like paper reacts to cars speeding by. (Just to make things even better, the Machinarium soundtrack is also beautiful)

http://machinarium.net/demo/