The latter were heads of very powerful states, and the former are simply transnational terrorist groups with no state behind them. Sure, ISIS has a state of sorts, but it cannot exist like Iraq and Syria did. For years, those two states lived in peace with the world, and no one was waging war on them. As long as ISIS exists, much of the world will be attacking it.
The Israelis fear states and semi-states. They do not fear isolated non-state terrorist groups. Hezbollah is now so heavily armed that it is more or less the armed forces of Lebanon, so this state within a state is an Israeli enemy. Israel does not fear Al Qaeda and ISIS because they think they can handle them. Whereas states like Syria, Iraq and Iran and de facto states like Hezbollah pose a real threat.
