The Internet Archive is expanding its Historical Software Collection to include a free Console Living Room beta, which recreates some of the best classic '70s and '80s video game systems on the web for the sake of preserving history. The library currently includes hundreds of games for the Astrocade, Atari 2600, Atari 7800, ColecoVision, and Magnavox Odyssey. Naturally not every game is available for every system and some games don't currently have working sounds, but things are still being tweaked.
Still, it's better than nothing at all, and future tweaks to the software should make it a more palatable experience later down the road.
You can check out the games here.