If you want examples of games that need a gamepad, brothers is one. Any game that has mechanics based on "rotation". Games that utilise more than 8 directional movement are generally going to play better with a gamepad. 2d platformers? No, not unless they are heavily reliant on analogue movement and even then you can often acquire greater precision using the tap method on a keyboard. Ask a high level Trackmania player if that game should be played with a controller, the answer will always be the same, absolutely not.