kinda.
The best solution, btw, is either a true 4way joystick or a set of oscars restrictor plates (might be andy's joysticks taht can switch easily... I haven't tried them)
but for the best software solution I've heard of
you can do this... for selecting up, press up, left, left, right, right. It will show up as up, not left, not right.
this will remove the possibilities of diagonals. Trouble is that it only takes care of one of two problems that you get when playing with a 8way joystick on a 4way game.
1) Original game doesn't know what to do with a diagonal, so it has weird and random effects (try playing frogger with diagnols. you get extra jumps at weird time).
this is taken care of from the above hack
error 2) Dead zones. This is now areas that don't do anything. You think your going up, but you really are going up and a little left. 4way joysticks usually have an extra nib or something that will make it easier to go up/down/left/right so you have a better feeling for the controls.
btw, I would prefer to use a keyboard or buttons then an 8way in many games... even with the up/notleft/notright hack.