You can still pay all c64 games (although it takes some effort) and they are 30 years old
There are games that are even older still, for instnace the original Adventure (father of all adventure games) is still possible to play, and it was released in 1977 (35 years old!).
The biggest problem I think is not the games themselves, but the input. For instance playing any N64 game is hard because available controllers are not that appropriate. It will be even harder for wii games, guitar hero etc. I think that 50 years from now, there will still be many games of today available, especially PC Games, although they might not be super easy to run.
While games as a medium is special in hardness to preserve, other media such as music and movies are not all that different. For instance many early movies have been lost due to the films being very inflammable.