How do you mean “limited”? Limited in time? Or geographically? Or in intensity? There were seven major Crusades over 195 years. ISIS has exists as ISIS only since 2013, although it did evolve from other terrorist groups going back to 1999, so time-wise ISIS in some form has existed for maybe 16 years. As for geographically, the Crusades took place in just as wide a space as ISIS. About the only other way the Crusades might be considered limited is in intensity. But this is very hard to judge, since modern day terrorism benefits from instant news coverage, in which a single beheading has an instant and wide-spread impact. Also they did not have access to the kind of weaponry that ISIS has today. But even still, I think it would be hard to make a case that there was not as much killing during the Crusades as ISIS has done.
The Crusades proper involved a very limited area; basically the coastal area of what is now Syria and part of what is now Israel. Granted, in the First Crusade and, I believe in the Fifth, the Crusaders went through Asia Minor on the way, recovering some of the Byzantine lands for the Byzantines along the way. There was a brief foray near Alexandria in Egypt. Christian Armenia also recovered some of its territory.
But always, the “Holy Land” was the ultimate objective, particularly Jerusalem, and most of the actual fighting was in a very small area. There were times when Crusaders were actually allied with local Muslim rulers against other Muslim rulers.
There were truces and treaties; sometimes kept and sometimes not kept.
It is said that the First Crusade was likely the bloodiest of them, but no accounts of it are universally agreed upon. But for the most part, Crusaders did not kill or even dispossess the inhabitants who did not resist. It was just as feudal in the Levant at the time as it was in Europe, and the local lords, whether European, Arab or Turk, depended on the peasantry. Some historians maintain that it was a matter of indifference to the peasants who the rulers were, because the obligations to the rulers were the same, no matter who they were.
No small number of Crusaders, we are informed by historians, intermarried with the Levantines.
The Crusades very much resembled the war and peace of the time, both in Europe and in the Middle East, until the very end, when large Turkic “nation states” made short work of both Crusaders and Arab rulers. The Arabs, of course, got the worst of that because they had no place to go. The Europeans could take to their ships and leave…and did.