You'd be better off asking in what ways are they similar, the full extent of which would pretty much be that they are Sunni Muslims and claim the Caliphate.

In no other measure that I can think of are they in any way similar. The Ottomans were a recognized state, a world trading power, had a highly centralized government, were extremely tolerant of other faiths and minorities, cooperated with Europe (particularly France) spread art and culture, eventually in the 19th century carried out a project of modernization aimed towards something like constitutional government and technological advancement.

I could go on and on. Your other comment was about end goals and violence. I don't see how they shared any end goals. The Ottoman state was definitely violent but no more so than any other world power of the time. They're somewhat infamous for fratricide when the Sultan succeeded but in exchange for royal death they managed to avoid the civil wars of succession that plagued virtually every European power and thus certainly had less internal bloodshed than, say, France, England, the Holy Roman Empire, the Italian States, Spain, Austria, etc.

Could you clarify your question a lot more? There's about a dozen different things you could be asking.

Im sorry, but this is a near impossible question to answer, a bit too much like apples and oranges. Firstly, almost anything regarding ISIS and their goals would be breaching the 20 year rule, as the original group which began ISIS, The Islamic State of Iraq, only began in 2004-2005.

Second, they are a warring militia which has gained some predominantly Sunni territory in Syria and Iraq in the absence of a strong state, certainly they are the most powerful militia in the area, but they remain only a Sunni Islamic fundamentalist militia. The Ottoman Empire was a massive, powerful, and quite pluralistic place which at times over its more than 500 year history stretched from North Africa to Eastern Europe to Persia.

As for the siege of Vienna, which one? The Ottomans were at war with the Austrian Hapsburg dynasty for around 300 years, and capturing Vienna was a strategic goal of theirs since the first siege of Vienna in 1526. They would be defeated in their final siege of Vienna in 1683.

And, probably most importantly in terms of end goals, this is truly impossible to compare. ISIS's stated goal is the resurrection of the Islamic Caliphate, a goal which they claim to have achieved with Baghdadi's declaration of himself as Caliph (again, this all breaks the 20 year rule). The Ottoman Empire WAS a Caliphate, with the Sultan of the Ottomans also having the title of Caliph and spiritual leader of Islam.

At the end of the day, like I said, this is impossible to compare. However, if youre looking to learn more about the Ottoman Empire and Caliphates (theres been quite a few) and a history of the region in general, I would suggest first Hourani's History of the Arabs, the classic Middle East history book. Also, some specifically Ottoman history would be much of Bernard Lewis' earlier works (before he gets too political, so anything before 2000).