Antique Definition: a work of art, piece of furniture, or decorative object made at an earlier period, and according to many customs laws, at least 100 years ago.
But that definition has begun to change in our increasingly disposable society.
A car is an antique if it's at least 25 years old., so I guess it depends on the item in question. If you consider your game a work of art, then maybe it needs to be 100...if it's a driving game, only 25?