What set the Yugoslav partisans apart from other resistance movements in occupied Europe during World War II?
Yugoslavia was overrun in 1941 in mere days by the German Army, and most people forget what a young country it was, having been formed just after World War I, and encompassing eight formerly separate nations and peoples. Once it was conquered, Hitler expertly played local nationalist movements against one another, allying himself with the culturally and religiously similar Croatians against the Serbs and others.
So one thing that made Yugoslav partisans different was the fact that they were not only fighting against the Germans, but also against each other, and those rivalries ran bitter and deep. They were also, in general, much more independent, and worked to a lesser degree with the Allies than did their counterparts in France, for example. It should be noted, however, that Croatians, Macedonians, Serbs, Slovenes, Macedonians and others all participated in Tito's resistance.
Tito's partisans in particular were also tied to loosely to a Marxist/Socialist ideology, where the vast majority of the other resistance movements in Europe were simply anti-German in nature.
I would say that Tito was a singularly effective and popular partisan leader, whereas the other movements were typically only locally organized, without such a strong central authority to lead them.
Lastly, This resistance movement, after 1944 turned into a full-fledged army of more than 800,000 soldiers, organized into divisions and field armies that fought not as guerrillas, but as regular conventional units.