Not sure if anyone mention this yet, but video games are more taxing for the CPU (ram and etc) than movies. You have to build or modify a computer to play some PC games in their medium settings at 720P or get a specialized PC/gaming machine. For movies, you need a blu-ray player for blu-ray discs but you don't need a specialized blu-ray player to watch Pacific Rim on your HD TV at 720P. Blu-ray drives/players are also much cheaper than PCs that can handle a modern graphically intense game in medium settings.
You also mention every game can be played by a PC, too, if the PC is an expensive gaming device or if you have the know how to make your own. Even if video games would end up in one platform like the PC and a company made gaming PCs cheaper, then expect another PC company to make another gaming PC to have more power or abnormal controllers. They would try to create exclusive video games for their platform too. In fact, what I described is almost similar to Playstation and Xbox.
