Have you checked if it is the spark plugs or fuel delivery? If you unplug a spark plug wire and lay it on the engine block (away from the battery), turn the key while having someone else check if they can see a spark coming from the wire. If a spark is visible, that means fuel is not being delivered to the engine properly or not at all.

I'm betting the little black box inside the bottom of the distributor has failed and needs to be replaced. Usually when this is the case the vehicle has had a sporatic starting problem for a short amount of time where it starts right up almost always but now and then takes a few tries before it starts.

Does have a spark, How about fuel delivery, may be a cloged fuel filter or faulty fuel pump.