Without the Crusades, we'd all be speaking Arabic.
In my opinion, the crusades had little military significance in stopping Muslim expansion. The muslims reached their highwater mark in Western Europe (Spain & Southern France) 300 years before the first crusade, finally defeated in France by Charles Martel. And they were at the gates of Vienna (Ottoman Empire 1683) long after the last crusaders had left the Holy Land at the end of the 13th century.
The end of the dark ages, which included more religious, personal, and academic freedom, sparked technological advancements and thriving economies in the West, even more with New World wealth and resources. The muslims suffered from similar issues that plunged Europe into the dark: internal corruption, disunity, and the darkness that comes without freedom. This was more critical in keeping them from advancing further into Europe. Only now with oil wealth have they been able to rise up again and be a threat to the civilized world.
Had Europe (and all Christian states in the 7th century) been more unified at the beginning of islam’s adventures, it could have been easily squashed. Instead they were more concerned with destroying political rivals or competing theology rather than the real threats.
Its good to learn from history and hopefully avoid the mistakes of the past.