Hi, I've discussed this question a lot as to why WWI was the first 'real' world war. I'll just copy and paste the answer I gave last time with some edits:
The reason we call them the First World War and the Second World War is because that's what people at the time called them and it's what they've been called for going on a hundred years now. Obviously they weren't the first war that took place across 2+ continents or to involve two powers on 2+ modern defined continents but that's not the point: That's what people called them, it's what they've been called for decades, that's what they're called -- first by the German Ernst Haeckel in September 1914 and again by Charles à Court Repington in 1920. There is no international organization or cabal of historians 'naming' things -- it's just we call it what people call it and things stick.
Another reason, and perhaps the most common modern justification though, is that those wars were European wars which just extended to their colonies which happened to be overseas. They weren't 'global' conflicts in that respect they were localized conflicts with localized goals which just had extended fighting -- every single war you listed fits that bill. Outside of the Mughal Empire in the 7 Years' War they're all European powers. The First World War was the first truly global war which hit every single continent. Japan and China and East Pacific colonies, India, Australia, South, East, North, and West Africa, Eastern Europe, Western Europe, the North Sea, Brazil, Central America, North America. Every single corner of the Earth, all from independent or quasi-independent dominions (Australia, Canada, South Africa, New Zealand) operated as independent military entities and as independent government actors. That had never been done before, ever.
You wouldn't call the Gulf War a 'world war' even though it was the U.S. & Friends (America & Europe) vs Iraq (Asia), would you? It had global participants, significant casualties, etc. It's the same thing here honestly: None of those wars you linked involved the popular participation of everyone everywhere even though they, at times, involved some powers from not-Europe and fighting in not-Europe. A 'world war' is not just who is fighting but scale. No one was unaffected by WW1 or WW2. Yes it was started in Europe but its participants not only went beyond Europe those directly and largely affected were as well. 1.5 million Indians would volunteer to fight, America drafted nearly 3 million people, 40% of the Australian male population would enlist, fighting would occur off the coast of Brazil and just about all of Central and South America would come on the side of the Allies as independent, sovereign states. China would send tens of thousands of men to contribute to trench building and also providing supplies while Japan seized numerous German colonies in the Pacific in blatant expansionism. Africa was a theater of independent, quasi-independent, and European fighting forces that raged throughout the war.
Numerous, global belligerents had numerous goals (America expanding trade power in the post-war world, basically any laundry list of European reasons, Ottomans pushing into the Caucasus' of Central Asia and firming their grip on Egypt in Africa, Germans expanding colonial gains by creating a continuous German state across about all of South Africa, Japan taking control of European pacific holdings and trying to force China into basically a protectorate, Australia/Canada/New Zealand/South Africa all developing national identities and using the war as justification for true independence, dozens of Middle Eastern tribes tearing the Ottoman Empire apart for independence, Slavs fighting for independence and unification from the Austro-Hungarians and the Russians trying to enforce such, etc.
That's really what separates it from every other global conflict before it (though the 7 Years' War and Napoleonic Wars are the only ones which can really be shoehorned into that category) -- it was not the Brits fighting in Southwest Africa they were Boers, Rhodesians, and Zulu's. It was Indians going to fight for Britain, not Brits. You see where I'm going with this? Nonetheless even if we go beyond this providing material support alone constitutes direct involvement and impact.
That's really the point. Only a select few people in the world were totally escaped from the realities of this war whether it was direct fighting or economical. This type of global participation was unprecedented and you will never find a war like it because every contender for 'world war' before it (7 Years' War and Napoleonic Wars in particular) are European powers fighting over European 'things' in European led colonies. Not this time: Belgium, Romania, the United States, Australia, India, South Africa, the Ottomans, Mideastern Tribes vying for independence, Hejaz, Japan, Cuba, Costa Rico, Siam. 65,000,000 combatants would participate in the war and 37,000,000 people would die. It was not a European war between European powers for European goals it was a global war between global powers for global goals with significant global fighting between non-negligible sovereign global peoples -- the African, Middle Eastern, and Asian theaters alone justify this point imo without even touching America or Europe!
TL;DR:
It's not called a 'world war' because that's not what people call it. It's really that simple. They're called the Napoleonic Wars because they're centered around Napoleonic France and that's just what people call them. The World Wars are called the World Wars and have for over 70 years so that's what we call them.
The phrase 'world war' comes with some implications though. These previous wars were European wars between European powers for European goals. WW1 and WW2 especially were global wars with global participants for global goals like never before.
Deaths and how many continents one fights on doesn't mean it's a 'world war' because that's a very colloquial term -- it implies a level of scale. Like I said above: The Korean War had belligerents from 4-5 continents taking place, Roman wars would have belligerents and fighting from Europe to Africa to Asia. I know it's counterintuitive but 'world war' isn't about the 'world' part but an arbitrary level of scale which we, as a society, place on it. It implies popular participation of everyone everywhere; not just fighting everywhere but sovereign peoples from all over the world taking place in the fighting in some willing fashion or being directly affected by it. WWI did that like no other war before it and WW2 beat that even more.
Where I got all these silly ideas from:
Peter Wilson, The Thirty Years War: Europe's Tragedy
John Lynn, The Wars of Louis XIV, 1667-1714
Christopher Clark, Iron Kingdom: The Rise and Downfall of Prussia, 1600-1947
David Chandler, The Campaigns of Napoleon
Hew Strachan, The First World War: Volume I: To Arms (specifically his chapters about 'the Dark Continent', the African campaigns)
"World War" was more a popular term than anything else, there are many other wars which covered an even greater geographic area than WWI/WWII.
Thousands of years ago Alexander the Great lead armies from Greece into southern Europe, then to the middle East, Africa, Central Asia and the Indian subcontinent.
You can look to the Mongol Conquests, which completely engulfed Eurasia for centuries, and included battles all the way from the pacific rim Chinese coasts to the Mediterranean and Baltic regions of Eastern Europe.
The eighty years' war, the war of Habsburg succession and the seven years war all resemble WWI, insofar as much as they have European powers feuding, involving their colonies, and projecting force through worldwide naval activity.
While WWI and WWII certainly were greater in scope and scale due to technology, one could easily argue that the Alexandrian, Roman or Mongol campaigns, occurring centuries before, were just as significant on as a % of world population affected or conquered.