Can you copy a game if the copyright has expired

If the copyright on a game has expired, then it has passed into Public Domain and can be copied, yes.

If you are talking about computer games though, keep in mind that depending on country, copyright expires after 50 to 70 years after the death of the last creator, and even then it can be extended. In short, no video game's copyright will have expired, only ones which the creators have freely given up all rights to.