If you've replaced the battery with a known good one and all the electrical systems are working EXCEPT the starter, I'd suspect either the starter has failed, or the solenoid has failed.

If you were cranking with a weak battery, that can be just enough to push a weak starter/relay over the edge.

Once you get the car starting, check to make sure it's charging. With the engine off, your battery should be ~12.8V or so, with the engine running, you should be somewhere close to 14V if the alternator is working properly. Given that the car sat for a long time, it could have just been a failed battery (has happened to my 500SL twice due to sitting).