Strangereal is the fan-given and, later on, officially-endorsed name to the universe featured in most of the Ace Combat games. In Strangereal, Earth has a completely different structure, with different continents and oceans, whereas the other universes' Earths all have a similar structure to the real one.
Strangereal's Earth also features a completely different culture, especially concerning military. While humans on the real Earth typically fight in hand-to-hand combat or with infantry weapons, the seemingly most-common form of combat on Strangereal's Earth is aerial, usually involving fighter jets. Additionally, military budgets are concentrated more towards an air force than an army, and most countries put their focus into building a massive heavy command cruiser or other form of large aerial ship, or even spacecraft.
Some countries on Strangereal's Earth make parallels to the real Earth. For example, Osea and Emmeria show similarities to the United States of America, Yuktobania and Estovakia are similar to Russia, and Belka is especially close to Germany.
Joint Assault universe
The Joint Assault universe is the fan-given name to the universe featured in Ace Combat: Joint Assault. Of all of the continuities in the series, this universe is the closest to the real one. The only major difference is the sequence of events following the financial crisis of 2007-08, which serves as the plot of the game.
Assault Horizon universe
The Assault Horizon universe is the fan-given name to the universe featured in Ace Combat: Assault Horizon and Ace Combat: Ikaros in the Sky. This universe has a similarly-structured Earth to the real one, but the history of the Assault Horizon Earth involves many unique events over the course of decades in the modern era. Additionally, the military budgets of the world's superpowers seem to be focused more on aviation than in the other branches, mirroring Strangereal.
The Infinity universe is the fan-given name to the universe featured in Ace Combat Infinity. This is the most unique of all of the continuities featured so far in the games, because it combines the real Earth with elements from the Assault Horizon universe (most notably aircraft such as the ASF-X Shinden II and elements from Strangereal (most notably the Ulysses 1994XF04 and Stonehenge).