Its the multiplayer is what makes this game great.
Gameplay: Halo 3's story may be short to some but it does not mean it is not fun to play through especially with the addition of xbox live co-op, the story may seem confusing to the majority of people who may have not played through the storys of Halo 1 & 2 but the singleplayer in Halo 3 is not the main thing that makes Halo 3 great, its the multiplayer. The multiplayer is different to what you find most other first person shooters which to almost all is a great thing, the mutiplayer is fun online but even more fun to mess around with friends on such as in forge. Forge mode which lets you create your own maps, but not like changing the landscape but changing the positions of things like weapons, warthogs, respawn points and even things like crates and gravity lifts, forge for some people never gets old and is a great way do have fun with friends by just messing around with it. The story may seem short but with one of the best multiplayers ever this game will keep you happy for hours.
Graphics: If you compare Halo 3's graphics to halo 2 you will be able to see a big difference and that Halo 3's graphics are now so much better. The graphics are great from the screaming grunts face to the blood of the dead brute cheiftain.
Sound: Halo 3 has probably the best music than any other game, its music may seem strange at first for new players but you will come to love it during the final minutes of finishing the fight.
Value: Halo 3 is worth every cent or p you pay for it, although (unless your a halo fan who knows the story) you probably will think halo's story isnt enough if you don't have xbox live.
If Halo 3 is not on your collection make a little space for it and go and buy it, you wont be dissapointed.