Underrated niche games you wish other anons would know of.

Patrician 3 is easily a hidden lost gem from a past time, it is the best the genre has ever gotten to. It has great multiplayer and still functions on modern systems.
Its a little game about being a trader in the Hanse, its great for competing and just hanging out. Its hard to describe but it scratches a itch you won't really see elsewhere.
You build and buy ships, take over by force, go pirate, build workshops in towns, farms, churchs, hire and send armies and shit over the whole hanse, which is quite the extensive map even if the variety is low to only a few dozen goods and building types.
Naval fights feel great, specially vs other people.
It is old and looks ancient but in a charming way of good old games.

City sieges feel great to fight with a fleet, specially when the same city is already under attack by a fleet. Doing so while facing off another player is amazing, and easily my favorite part of the game, sinking eachother ships and competing over effective control of towns and ports to produce and profit off production.
The best game i've had yet was 6 players and lasted 12 sessions, 4 hours at a time on weekends. I have short of 6 thousand hours on this game.