If it says 'Disc not suitable for this system' this means that you Saturn is not recognizing it as a Saturn game. This could be due to a bad rip or a bad burn. You could try reburning it at a lower speed, but I wouldn't count on it making a difference.
If it says 'Game disc not suitable for this system' this means that you Saturn is recognizing it as a Saturn game but with the wrong country code for your Saturn. Change the iso's country code to match that of your Saturn using Satconv (DOS or Win32), reburn and all should be well.
Bad media, as in defective media, could lead to a sudden termination of the burn before reaching 100%, thus resulting in an instant coaster. I had that happen to me once before BURN proof technology came about.
did u check that the games suits your system before u burned
it(if not then guess ull have to patch it to suit your territory)
do u have it chipped and action replay cart to play imports
questions that need to be asked
check the image/game with satconv
to see what territory it is
then patch to suit your needs
the other cd u have stick it in your microwave(not white top ones though)(casue theyll do some damage)(or blow up)great fun and they all make differant patterns depending on the cd manufacturer (a couple of seconds will do the trick)