So just a little bit of XNA code:
if (this.IsActive && (Keyboard.GetState().GetPressedKeys().Length > 0 || Mouse.GetState().LeftButton == ButtonState.Pressed || Mouse.GetState().RightButton == ButtonState.Pressed || Mouse.GetState().MiddleButton == ButtonState.Pressed) || GP_state.GetButton(8) == ButtonState.Pressed)
{
Current_GameState = GameStates.Game;
bg_music.Play();
}
If something is done --> Switch to a different game state. Works with: Keyboard and Mouse, but not with the gamepad (which is new and it works with other games) So why does XNA not recognise it correctly??
EDIT: I do have a working solution and mark my own answer as soon as possible as right...