In November 1095, when Pope Urban II called for a crusade to the Holy Land, he believed that the crusaders would win resounding victories, and that in his lifetime the day would come when Western Christendom would take control of not just Jerusalem and other holy sites but entire Levant. But the First Crusade, and the subsequent crusades, became bogged down in a series of wars, massacres, conspiracies, riots, and assassinations which went on for two centuries, till 1291.
The high religious and political rhetoric of the crusades was not backed by wisdom, political prudence, and astute military planning. Even the high-ranking crusaders, the kings and the nobles, had a naive view of the region where they were going to fight. They were mostly clueless of the ruthlessness and military capabilities of their oriental rivals. Whenever the crusaders scored a military victory, they failed to build on it. With the result that the fruits of that victory would get frittered away. The crusades ended in a colossal failure: all the Christian kingdoms in the Levant, including the Byzantine Empire and the four crusader kingdoms which the First Crusade had won, were lost. There was a massive desecration of places of historical and religious significance, and a thorough decimation of the minority communities (Jews and Orthodox Christians) which had been living in the Levant for centuries before the crusades were even conceived.
The crusades in the East were undoubtedly a geopolitical and religious disaster for Western Christendom. The irony is that the only geopolitical success that the crusades achieved was in the heart of Western Europe. Pope Urban II had enjoined the Spaniards in 1096 that instead of marching eastwards, towards the Levant, they should complete the conquest of the Spanish territories. The reconquista went on in Spain till the second half of the fifteenth century when the Catholic Monarchs of Spain, Queen Isabella I and King Ferdinand II, won the kingdom of Granada. But Isabella and Ferdinand were not committed to taking back Jerusalem. Their priority was European internal politics. Another crusade in Western Europe that was successful in religious terms was the Northern Crusade, which pitted the crusaders against the pagan Slavs (Wends) and Balts and led to the expansion of Christian forces in the Northern parts of Europe.
The Spanish reconquista and the movement against the pagans might have happened even if there were no crusades to the Holy Land. It is not clear if the crusades to the Holy Land can be credited with the victories that Christendom achieved in Western Europe.