For me, i would get a Xbox 360 controller for "casual" racing games (the analogue L/R triggers are beasts, better than my Rumble Pad) or Logitech G27 (if your rich) or Driving Force Pro GT (on budget).
For flight games, i would get a decent joystick with the jet liner style thottle controls. From experience, these flight sims are dam hard to play with gamepad or keyboard.