It is just either a fancy patch for Halo 2 or Halo 2.5
All of the multiplayer maps are all of the originals from Halo 2 but changed slightly and given a different name. Example: Last Resort = Zanzibar but without the glitches and slightly changed, Valhalla = Coagulation but slightly different, etc...
Multiplayer is boring and repetitive with millions of fanboys and 10 american kids swearing at each other all the time. Also full of nooby weapons including: Rocket Launcher, Spartan Laser, Energy Sword, double wield shotgun's etc etc. Nice one Bungie, 3 years for a waste of time of noobyness and boring repetitive play.
Campaign is probably the highlight of the game, but is also ruined due to shortness, (you guessed it!) more repetitive gameplay. I could literally run through the first two levels without equipment or jumping. The plot is also not very good. It may as well be called Halo Online and not include a campaign because they just try and get that out of the way so that everyone can go online. Legendary difficulty is really easy, the AI are meant to work as a team and I completely forgot all about it before being reminded just now on Wikipedia because I saw no signs of it.
Graphics are practically the same as Halo 2 as well and there not that good any way in comparison to better graphics in games such as BioShock, Gears Of War, The Darkness, Call of Duty 4 and many others.
Any other gamer: Oh right, explain the campaign to me, I don't fully understand it.
Halo fanboy: There was a campaign?!? I was too busy being a n00b online with all the n00by weapons and making fun of people online because I think I'm hard because they can't see me or reach me and making fun of games that are better than this one I didn't realise.
little billy was a straight A student, turned in his work on time, always on time for school, and never fell asleep in class.
little billy now is a nocturnal energy drink chugging pasty white as snow trash talking FIEND that goes by an alias known only to him and other xbl affiliates.
lil billy will be missed.....
person 2: I hear they're releasing number 8 next winter. This one's being billed as "The Penultimate Gaming Experience of your Lifetime."
person 1: Man, I'd better go preorder mine now!
I look forward to laughing at the PS3 fans on that day.
PS3 Fanboy: "Stop overrating it!!!" *sulks in corner*
Gamer1:"Halo 3's out soon!"
Gamer2: "I know!" *Head explodes in excitement*
Gamer1:"They canceled Halo 3."
Gamer2: *commits suicide*
Gamer1: "Wait, it was a joke."
PS3 Fanboy:"Halo 3 is teh Suckzorz!"
Xbox Fanboy:"OMG STFU!"