Nice one insomniac
The replay value is very good first you get the story mode which is like a mix of half life, halo, call of duty, unreal and more. Basicley it takes the best bits from all recent FPS's and puts it together in a mostley linier great looking war zone in england where you fight an alien force, the chimera.
You fight a variety of enemies which all look great and are fearsome to and challlenging to fight. The difficulty is perfect, i played it on medium first and completed within about 2 weeks playing while also trying the online. I then played through on hard in about 4 days recently when i got my new tv and discovered the 2nd time is way bettter as you get about 4 new weapons which are bery cool, this makes the guns unmatched since perfect dark on n64.
Online is also really good when you find the right battles the possibilities are endless with such a great variety of guns and grenades theres always a new way to play as long as you not fighting uber players then its like just try not to die too much. You get medals for various things and its adds a sense of accomplishment and they look cool. Online rocks.
Yeh i prefer this game to COD4 its just awesome if youve not played it get it its pure fun and great looking.