Hey T-Octopus,
If you have an 8-way on your control panel then you can play Q-bert and Congo Bongo just fine. Go into the "Input this game" menu in Mame and do this. For joystick right, re enter it by quickly moving your 8-way joystick right and then down. If you do it quickly mame will except both inputs. For left hit left and up. For up hit up and right and lastly for down hit down and left. Setting it up like this will allow mame to only recognize the horizontals which is what you want for Q-bert and Congo Bongo. This is the next best thing if you don't have a 4-way mounted on a 45 degree angle. It works quite well.