Greater Diplomacy Hex Edition is so different from the other versions that I don't consider it a continuation of the series, but rather a very interesting offshoot. Its most prominent feature has to be the fact that it uses a hexagonal grid instead of normal tiles, but that's not all I packed into this monstrosity. There's 8 different types of units, 3 different types of resources, and naval combat exists.
Greater Diplomacy 3 allows you to save your game and load it in later, so you don't have to lose your progress if you need to turn off your computer for something.
Personally I think Greater Diplomacy 2 has too many provinces, making playing it feel less fun. It does feature a tutorial though, which is very helpful for new players.
Like Budget HOI4, you can play against the AI, but you can also play it with up to 8 other people! However, you all have to be on the same computer. It's not online.
A significant improvement to my first strategy game, and the first time I made an AI you can play against.
My first attempt at making a strategy game. It works, although not very well.