Destructoid doesn't think Halo 3 quite lived up to its predecessors.

The problem, then, is where exactly do you go when all you've got to do is cover a handful of unknowns? The game sarges onward on with battles that, in the end, remain largely irrelevant to the story; they happen and you move along towards what you're hoping will be a moment pivotal to the plot. It's bound to satisfy many gamers just looking for some good, solid action, but in an age in which engaging, well-constructive narrative is possible even beyond the big mystery reveals (or the "Would You Kindlies", which I'm demanding everyone call them), Halo 3 falls short. Story should remain distant second to gameplay, but not so distant as demonstrated by a game like this, particularly when the developers have had two previous titles to develop such a rich backdrop to build upon.

They gave the game a respectable 8.5 out of 10; the summary might be "flawed but enjoyable".