I don't belive you can patent gameplay. You can't say "I'm going to patent the idea that you all go around a board buying land and getting cash, if your player moves to someone else's land they have to pay them rent."

But you can copyright the artistic aspects of your game, like you can have the copyright to MONOPOLY and trademark the logo.

If you could patent gameplay there would be only 1 pong, which is a pretty basic idea. There are probably hundreds of pongs though.