(why didn't Gears 2 have 4p co-op >_<)
It doesn't!? *cancels pre-order in rage* 
You can shoot AI enemies in 5 player co-op in horde mode, which is cool. But the main campaign is 2p only like the first even though you have a FOUR PERSON SQUAD (so 2 AI's when online) for most of the game.
'tis really my only complaint with the game. I'm sure 2p is still a lot of fun like the first one. I've only had a chance to go through 1p, but I'm looking forward to going through it in 2p. But I can just imagine how much fun 4p would've been like Halo 3 when I watch me + 3 AI guys fight through these stages.
Back on topic, I like Halo's story. It might not be anything more than a videogame story, but I enjoy a worldview and mysteries in my action/shooter games. It gives me stronger motivations to shoot aliens in the face if done decently. Puzzle games, racing games, sports games, etc... don't really need plots, but FPS games should have them. Just remember to make all cutscenes skippable
