Every era should be represented with at least one or more events related to a major change of history. Every major event should have the chance to occur of 10 % per game If the conditions are fulfilled . For some variety and replay motivation and against boredom it should be a few per era. So this were my suggestions
Ancient Era:
The Ten Plagues of Egypt event / The submergence of Atlantis /The Storm of Sea Peoples event
Classical Antiquity: The Cimbrian War event /
The Star of Bethlehem event / The Yellow Turban Rebellion event
Medieval Period: The Scourge of God event /
The Black Death event / The Divine Wind event
Renaissance Era: The Little Ice Age event /
The First (Spanish) Sovereign default event
Age of Revolutions:
The Revolutionary War event / Golden Age of Piracy event / The Russian Marshal Mud event
Industrial Age: The Australian Gold Rush event / The Cholera pandemic event
Modern Era: The Dust Bowl event /
The Black Thursday event
Atomic Era: The Oil Shock event / The Great Smog event
Information Age: The Global Warming event / Total Internet Blackout event
I think these perpetuate a classic 'Civ' game problem: trying to make a specific game event out of what was historically a result of more general conditions.
Let's go down the list for examples:
Ten Plagues of Egypt, assuming it isn't a religious myth, may have been related to the second 'event' -
Submergence of Atlantis, which was almost undoubtably connected to the volcanic eruption of Thera that engulfed the Minoan settlements on Crete and what is now Santorini - the remnants of the original volcano. So, both of these have a 'popular' or religious component, but have the same root cause.
Storm of Sea Peoples and the later
Scourge of God are both 'barbarian' invasions/migrations which massively affected the 'civilized' kingdoms in their path. To these you might add:
Classical Era: the Gallic Migrations that affected parts of Europe ranging from Spain, Northern Italy, the Balkans to modern western Turkey
Later Classical: The Germanic/Scandinavian migrations that sent Goths into eastern Europe and Russia, Saxons into England, and Franks into France, among others.
Classical to Renaissance: the various Northern Barbarians that invaded the Chinese kingdoms/empires: Jurchen, Mongol, Manchu, etc.
In other words, Barbarians occasionally move in large numbers, and those movements, whatever their original reason or cause, have Consequences.
Black Death Event and
Cholera Pandemic are indications that Germs move like Barbarians, but occasionally with even more deadly consequences, especially in the lack of any knowledge of antisepsis or germ theory.
Spanish Sovereign Default and
Black Thursday were both 'economic' events, the causes of which (and effects, for that matter) have never been modeled
adequately in any Civ game: it will require an entire new set of mechanisms, and because Economics is so fascinating to so many gamers

most should probably be 'built in' to the game with only the results 'visible' to the gamer requiring his/her attention.
Russian Marshal Mud is another Normal Event - the annual spring and fall rains that flood parts of the countryside and make ground movement very difficult
every year. It only becomes a Major Event (and Historically Significant) when the people trying to move are Invading Armies who have made grossly inadequate preparations for it out of Ignorance or Hubris. Since Civ-scale games have no seasons and Civ in particular has no Supply Lines, this is a Non Event in game terms, unless you 'generalize' its effects in some non-historical way.
I hope what comes through is that many or most of the Major Events in fact reflect on-going problems that a gamer should have to face, but currently doesn't in the game. The 'Major Event' designation is due to outsized Effects of one of the 'normal' disasters, either due to a combination of other circumstances, the inadequate response to the event by the Civilizations involved, or the severity of the event itself.
I suggest that we need two things:
1. What this thread has been discussing, (and the Mod has partially addressed) a system of Natural Disasters, including some that are not Natural, especially:
Economics: in the form of the ability of governments (the Gamer, the AI) to Borrow money from 'banks' or other game mechanics, and them fail to repay, with 'natural' and usually to some degree disastrous, consequences. Also, as I have posted elsewhere, the Cycles of Exuberence that lead to Capitalism's Inevitable recessions, 'panics', depressions, etc.
Barbarian Pressure: specifically, some kind of Population Pressure that sends entire 'nations' of people Migrating en masse. In the game, a large area inhabited only by 'Barbarian' camps next to a border with a Civilization should spawn near-constant such pressures - think the northern Chinese border or the European Roman border, both of which required enormous expenditure of resources to maintain by the two strongest Civilizations in their areas/Eras, and both of which eventually failed in the face of the barbarian pressure - Major Events by any standard!
2. A Chronicle, Timeline, or other In-Game Events designator. This is pure 'Color' with no direct relationship to game-play, except that it gives a narrative to your game: a news sheet/book title you can display or occasionally refer to that tells you that Scythia Invades Egypt! or Plague Ravages Samarkand!, or Brazil Defaults, Markets Panic!
And with a certain set of in-game triggers, leaves you a list of Major Events directly related to the game you are playing:
The Ten Plagues of Persia
The First Scythian Sovereign Default
The German Marshal Mud (the infamous
Strassenverloren season)
I think that relating the Major Events(Disasters) to in-game events 'particularizes' them in a way that makes them more relevant, and making Major Events a product of Both programmed Causes (weather, disease, economics, migrations) AND the gamer/AI's reaction to them will make them more 'real' to the gamer - and possibly teach the lesson that Major Disasters come from Normal Disasters as a direct result of human actions and reactions - the Bad Hair Day of God becomes the Wrath of God only after human rulers ignore the haircut...