Halo 3 is just like the other Halo games just with marginally better graphics.
Sound effects and music in Halo 3 is pretty good however some of the voice acting isn't very good, however I've heard allot worse voice acting in a game (Shenmue) so it's not that bad.
When it comes to the story I have to say once again I'm disappointed just like with Halo 2. The story isn't very interesting and at times it's downright boring and confusing. The ending is kinda anticlimactic after all the hoopla and hype about "finishing the fight".
Overall I would say Halo 3 is a good game but the gameplay is getting very stale in my opinion and if there is a Halo 4 I hope they overhaul some things and at least try and keep this game fresh. In the end for people who have played Halo 1 & 2 Halo 3's gameplay and story will seem boring and uninteresting throughout most of the game. And for those who aren't Halo fans and wounder what all the hoopla is about Halo 3 wont make any new fans out of these poeple due to the fact that it's the same as the other Halo games.