The Ancients? They were aggressive. It's a bit off topic, but I would like to say that the Ancients are another extraterrestrial species designed very well by Volition. I have always read stories about other civilizations, disappeared many thousand years ago, but they were all about a pacific civilization, crushed by another one, the enemy. The Ancients are realistic. A civilization with an expanded Empire, aggressive and overconfident. In Inferno R1, what remains of the Ancients should have been another opponent....fair thing to me.
In FS2 there's an Alliance...Terrans and Vasudans are supposed to work together...that's why we can easily consider them similar. I would like to mention, however, different kinds of behaviours and how the Vasudans face death. There are no "Oh my God!" and "What the hell are you doing? Help us!!!", typical of Terrans... there are sentences like "Avenge me!" and "Long live the Emperor!" that come from a different species, a different way to see ourselves, to see the others, to consider Life a gift.
That's probably why the HoL lasted too long, even if it wasn't as armed as another group of rebels like the NTF: with most members ready to sacrifice their lives, the HoL was able to resist against coordinated attacks for a long time. Terrans are always ready to collaborate and rarely sacrifice their lives in order to save comrades or kill enemies.