what are the best Simulation games to ever be released?

Gotta put Rimworld Out there if we're talking about sim games

Kerbal Space Program. It is a sandbox game where you assemble parts to construct custom spacecraft designs and fly them. It manages to combine the sandbox construction genre with a flight simulator with orbital dynamics. In addition to rockets, you can build planes, rovers, satellites, landers, stations - and with mods, even boats and submarines.

Unfortunately there were some labor issues a couple years back and most of the original dev team quit. On the other hand, that means you can pirate it and not feel bad.

Does Crusader Kings count? It's a dynastic politics simulator

Frostpunk is a fantastic city sim. Gotta survive a harsh eternal winter like snowpiercer, but all you have is a steampunk coal generator to keep everyone warm. You have to keep track of working hours, choose to allow child labor or not. Waves of refugees show up and burden your supplied leading to factions forming and murders unless you handle it.

It's a super cool concept that's very replayable.

Trailer

Also all your people have names and families and jobs, so losing them actually has some weight to it.

The expansions are all alright, each one has a focus on a different part of the story. One is after the main story and is about the politics of the different cities and factions, one is another city that failed, one is about building the generators, one is about some scientists that have to preserve a seed bank (really cool because you don't start with any workers, so you need to automate fast. There's also a "you can eat the seeds, but that could doom humanity in exchange for your survival" thing).

I'll be that guy and say Dwarf Fortress is cool, good, and free. It's been in active development for like 15 years by two dudes, and straddles city builder, management sim, and rogue-like. Fabulously complex and engaging if you can get into it, and it's not nearly as hostile to learn as the zeitgeist suggests. UI is famously janky but alleviated by a host of 3rd party tools, and a paid version is being developed that is re-tooling everything to be much more functional out of the gate.

The Championship Manager/Football Manager series is my favourite. But it is hard to recommend as it is a yearly release kind of deal. I am hopelessly addicted to them since the early 00s. Best sports sim games by some distance.

My personal favourite is definitely Euro Truck Simulator 2. It takes the good parts of driving long distances, giving you time to yourself just to think, and strips away the annoying bits like the lack of comfort and the cost. My dream game would be ETS 2 with AAA budget, but sadly it'll never happen. The main downside to ETS 2 is that it makes me want to buy a third monitor and dumb peripherals.

It's certainly unlike any of the other games that'll get mentioned, but The Sims (and to a lesser extent its sequels) is undeniably one of the best.

Victoria 2 is essentially a geopolitical simulator set from 1836-1936. The core mechanics are centered around economics, which is a very in-depth system, and influence. Diplomacy and warfare are somewhat lacking as the game hasn't aged that well. Compared to most other Paradox games, I'd say it fits much more into the "simulator" genre than the strategic sandboxes like HOI4 and EU4.

SimAnt

Mario - Italian simulator

An old 2002 game that I think really held up is Sim Golf (from Sid Meier). I still enjoy installing this game and playing it every couple of years. You basically design a small golf course and tourist area. But the best part is that you also create a golfer and can play the courses (including through Tournament events), and it has a pretty impressive golf mechanic (though few are better than the more recent non-Simulation game Golf Story).

My favorite part is that you can customize what the golfers say in text above their heads when they do certain things (hit the ball into the rough) or encounter certain objects. They can end up shouting things like "Oh Shit!!" when a ball almost hits them. I always found that to be enjoyable.

il-2 sturmovik 1946.

No idea if it's still decent, but I played hella Railroad Tycoon back in the dial up days

RollerCoaster Tycoon 3 (relevant)

Railroad Tycoon 3 is still the best logistics/industry game I've played. You build tracks between cities and factories/resource extraction points, then run a train company in a simulated market against decent AI ones. The economic model is great. Industries evolve organically in response to the unit price of goods. As wonky as a game released in 2004 is, it's still the best logistical train game and economics sim in my opinion.

Startopia isn't the best, but it's pretty awesome and it had groundbreaking mechanics for its time (like the Bio-deck). Also, look at that dope intro video, inspired by 2001.

Sim Tower

Grand Tactician: The Civil War is a game in early access that could be described as a Civil War simulation. It sees you take on the role of either the Union or Confederacy starting from secession through every single day of the war.

It has the most detailed backend I've ever seen on a wargame. When you click to tell your army to go somewhere, the game determines how long it takes your order to travel there (telegraph offices are pretty strategically important for this reason), and then your army will board a train if they can or else march/camp based on the time of day (though you can force march them if speed it vital). The distribution of rifles/muskets to your soldiers is tracked per-unit, as well as supplies and the ability to forage, and the game even tracks what state your volunteers/draftees are coming from, and your support back home will be effected by the casualties.

The most interesting thing to me is the game's "technology tree", which is represented as a series of political decisions that lead from one to another, which tell the story of America's economy getting industrialized and its politics getting centralized by the war effort. You start off by issuing the first greenbacks and activating the militia act to raise three-month volunteers, and you end the game taxing state-issued currencies out of existence and instituting the draft. And then you have to reform the draft because the first version had a lot of loopholes for rich people to get out of it.

The game ends up being pretty materialist thanks to its details - good tactics can win a battle, but the war is won by railroads and rifle factories. There's even some alt-history scenarios you can get into if you want - it's not as wide of a sandbox as something like HOI4, but European and Mexican intervention in the war is possible, and the alignment of some states might shake out differently based on your early decisions.

Which is the one that's the dynastic inbreeding monarchy simulator?

Flight Simulator X & Nascar Racing 2003 season/iRacing