trader/warrior
Deity
My main take is that IS cannot be even compared to Taliban or Al Qaeda. Former never aspired to created Caliphate, while latter never managed to capture a state of their own.
Technically, IS is Al Qaeda who have captured a state of their own, at least Al Qaeda al Iraq. As an organization a direct line can be drawn from Al Qaeda in Iraq to the IS.
The Islamic State of Iraq, led by Al Qaeda al Iraq formed and supported the Al-Nusra Front in the Syrian civil war, leader of AQI Abu Bakr al-Baghdadi and later "Caliph" announced that the two would merge to form the ISIL while al-Zawahiri of "vanilla" Al Qaeda denied this leading to a split between the two.
A lot of things have probably changed within the organization, but at it's base IS is the very same organization that was conducting attacks in Iraq over many years.