Not the best in the series but by far not the the worst.
Out of the story I think the "boss" fights they had were lacking as it took no skill at all to do them but I do not see Halo as a game that should have bosses..I say this because they tried that in Halo 2 and I did not like it at all so I am glad they took it out of Halo 3 but wish they could have made another unique ending but the current one they have works.
Now multi-player is the same as you would expect but with many new levels along with fun game types. The new vehicles are fun but lacking the new Human helicopter in multi-player. Let alone the new weapons are great...nothing is what as fulfilling as catching a sniper or let alone anyone off guard and torching them with a flamethrower. I have read many other reviews of people saying that the game sucks...compared to the hype. Well the hype is there so you will get the game and enjoy it. Do not envision games as being the holy grail as it will never happen...to your high expectations.