Gears of War 2 was great from a gameplay stand point, and as a sequel, it improved on every element of the first and addressed almost every issue. But from a storytelling stand point... well, lets put it this way. I didn't know it wasn't set on Earth until somewhere in the middle of the second game.
So unless I drank some paint thinner and zoned out for the first game, someone fucked up. There are pieces of a good story here, they're just not assembled very well. I've heard plenty of complaints over the plot having no real direction and being full of holes and head scratching moments, and I agree. Like, the leader of the Locusts being a hot British woman with messed up skin, when Locusts are really ugly.
Your right, that makes no sense, but look enough, you'll find clues and hints that make sense of it, but the 'answers' were not fully implemented into the game. It's like they had all these great ideas ready, all these plot arcs they wanted to get in, and managed to start on some, but never even got half of them rolling, let alone tie them up.
Plus it doesn't help it's a brown and grey shooter with space marines fighting aliens. Thats guna handicap ya from the beginning.