Maybe the best game I've ever played
There are some things that are a little annoying - like the Mako and some occasional graphics glitches - but this can all be ignored for the incredible story.
I honestly don't know what gamespot was thinking with an 8.5 - the reviewer must just dislike sci-fi. The production values for this game are awesome - including the voice dialogue which is excellent.
Ignore the gamespot score - f you are looking for a good involved story with fun fighting - pick this up. If you are looking for a shooter like Halo 3, then I'd steer clear.