Many PlayStation 2 games which were programmed to use the analog functionality of the PlayStation 2 controllers buttons will not accept non-analog input therefore Sixaxis or DualShock 3 controllers must be used (though this could potentially be solved with future firmware updates).
Many PlayStation 2 games that were designed to utilize the analog functionality of the PlayStation 2 controllers' buttons will not accept non-analog input, therefore requiring the use of Sixaxis or DualShock 3 controllers. This limitation could potentially be resolved with future firmware updates.