It's all about the atmosphere!!
This is neither St. Peter's in Rome, nor Notre Dame in Paris; this is all about the feeling! From the very first step in the courtyard, it hits you and hits you hard, the music, the incense, the prayers being cried out in multiple languages, the expressions on the pilgrim’s faces. The mood is very reverent, this is where Jesus was crucified, buried, and resurrected. Even if you don't believe, one can't deny the feeling, unlike any other place in the world.
It gets packed quickly so try to go first thing in the morning. As with most sites in Jerusalem, dress respectfully, cover your shoulders, pants or full length skirts, absolutely no cleavage, I saw one woman who was asked to leave!
It's free, doesn't cost a dime to get it, if you want to light a candle, the local priest expects and offering.
I recommend walking the Via Dolorosa first; no trip to Jerusalem would be complete without it.