PSX2 gamepads to the C64 for any other game.
Additionally this interface can score with a few additional features:
Two firebuttons are supported, which is needed for Shredz64 among others
The analog stick can be used, if of course only digitally
Since the PSX controller has 4 firebuttons, the above two firebuttons are again assigned with continuous fire.
You can program macros. So you can store sequences in the adapter and call them up at the push of a button (with the shoulder buttons).
And an important feature for me personally was that you can play with the PSX2 controllers, which feel very good in my hand.