*shrugs* i got no idea, i played the original on PC and didn't get why it was so great... i liked the Flood, but then again i'm a fan of ALIENS and the Tyranids from WH40k so that just opened up a whole other level 'fun' guessing games and scifi horror...
i pretty much blew it off as a series since my primary experience was a 'meh' ALIENS wannabe game that didn't have the balls to be really gritty or Star Trek knock-off that didn't get the memo about being 'nice' with the alien speices in the universe, take your pick... and i was dragged to a house full of 10 guys on fridays to 'play' LAN games when i had no idea how to operate an Xbox controller and they literally just dropped me in a game with nothing and the name 'Lag'... *clicks tongue* yep, rain of granades!!
i think the only time i gave it any credit was when my GIRLfriend/roommate in the Navy went OFF on me for calling it lame... i got to enjoy 5-6hrs of her ranting about the complexity of the story, the back story, the books, the universe, and i really by the end of it i thought it'd be interesting if THAT was what i was getting when playing and not... Halo .-.
suffice it to say Reach gave her an anurism and she finally understood why i had a deep hatred for the AVP movies...
honestly, its only good as a PvP thing in my opinion or meh co-op... as me and her blew up horde after horde of supped up goons after she beat it to make her feel better... but as a 'game' or story in general *shrugs* don't see why its that great when there's other stuff out there that's done it better .-.
maybe its just the supersolider idea that's not space marines *shrugs* and shiny?