you're on the right track. you need fuel, spark, and compression. you're missing one of the three. sounds like you have spark pretty well covered. when you turn the key to on (the cluster lights up, but before you try to start it) do you hear the fuel pump whirring?

HEY here's a stupid question. what year lude and is it an original key or a hardware store copy? the newer ludes have a chip in the key (immobilizer) without it, the car will crank but not start.