Even if we imagine some 'universal game binary', games are never going to be portable the way other media is. A movie is basically just a rectangle with some moving pictures accompanying some audio -- it's really easy to create a standard format that any movie can be shoved into. Video games, however, are much more dynamic. Video games require all sorts of complicated input devices – gamepads, joysticks, touchscreens, mice, keyboards, microphones, cameras, accelerometers, infrared sensors, etc etc etc.

You can still play old video games in emulators, but you are usually using an approximation of the original input device. This isn't such a big deal with older, simpler games – playing a SNES game with an Xbox controller is a good enough approximation of the original experience. But newer innovations like the Wiimote, Kinect, VR headsets, etc will make it a lot harder to play games made for them in the future. In 50 years, you'll still be able to boot up Wii Sports in an emulator, sure, but will you be able to find a good proxy for a Wiimote?

"will you be able to find a good proxy for a Wiimote?"

I'm betting I could print it and hack something together from some hobby electronics kit if I really wanted to.

But you are absolutely correct. There is a category of games for which the complete experience is unseparably attached to the original substrate.

On the other hand, keyboard and mouse driven games are fairly maintainable accross platform generations.