Saladin took Jerusalem in the Second Crusade, specifically in October of 1187. In the Third Crusade, Saladin started off in control of Jerusalem and Richard the Lionheart abandoned his marches on Jerusalem upon signing the Treaty of Jaffa. As a result, Saladin never lost control of Jerusalem during the Third Crusade and never had to retake it.
The fourth crusade was a children's crusade. The children set off to take back Jerusalem which was under control of the seljuk turks. The children never made to Jerusalem but instead attacked constantinople on accident. They mistook it for Jerusalem. The children lost and the ones who escaped were tricked into being sold into slavery.
To some people it does not matter. But for Catholic people, this was a major event. The first crusade conquered Jerusalem. Jerusalem is said to be where Jesus died and then resuscitated. The four nobles that led the crusade then killed all people in the city and the survivors were sold into slavery.