The Sony PlayStation 2 Controller

It looks exactly the same. It feels exactly the same. It plays the old games exactly the same. You can even plug it into your old PlayStation 1. So what's different?

Well, it is pretty much exactly the same except that now the shoulder buttons and four face buttons are analog. They don't travel any differently, so the buttons still feel digital, but the controller can sense how much pressure you put on each button. This is probably in response to the Dreamcast's analog triggers which allowed for things like variable control of brakes and acceleration in racing games.

On the whole, not many games make use of the PS2 controller's analog buttons because they still feel very digital. It's difficult for a player to judge how much pressure they should be putting on a button. But, it's a convenient way for Sony to expand the capability of the PS2 controller while still keeping compatibility and the exact same form that players are familiar with.