Fred,
I had the same problem with my 98 Cherokee Classic. I also let it sit for about 2 years. All the electronics worked fine, air, windows, everything. I would turn the key.... and nothing. It was not turning over at all, no clicking, nothing.
I assumed what others have posted (battery connections, alternator). I checked all that, but still nothing. I then got under my jeep and bypassed the starter solenoid, and it started right up (only do this if you know what you are doing, don't electrocute yourself please).
This led me to believe that the problem was with the starter. Yesterday I replaced the starter, and it started right up with no problems. I know that Mopar has had issues with their starters and jeeps a notorious for electrical problems.
Good Luck