Oh it's been ages, but I seem to remember foreshadowing at the end of Gears 1 or 2 that humans were the invaders on Sera and the Locusts were the ones actually defending THEIR home from invasion of space aliens (eg: you) and excessive exploitation once humans started hoarding imulsion or something? Been ages though and I never played past 2.
Maybe I was just reading into it too much because it's the kind of twist I would enjoy.
The fact that I don't quite remember but I can recite almost every line of dialog from Xenogears and Final Fantasy IV only illustrates my stating that these AAA shooter games have weak stories that aren't memorable . :D