Halo 3 on xbox is an extremely entertaining game wither playing online or offline there is still a great time to be had. you can kick some alien butt on the campaign as masterchief and try to win the game on the four difficulty settings or you can play multiplayer with two people on campaign.
Online play is brilliant being one of the few first person shooter games that allows multiple people playing online on one xbox there is also great fun to be had playing custom games with freinds either online or offline and there is mythic map pack and other extensions that can be purchased from the online store. I believe that one great aspect of the game is the ability to make your own maps using Forge one of the options available in the halo 3 game.
Halo 3 is like other first person shooter but is way more customizable and fun wither you have xbox live or not their is still a great time to be had. you can kill aliens with freinds online or offline you can play custom games with freinds offline and online with game types and maps that you can make and edit and there is the theatre mode where it is possible to watch all the games youve played as a movie that you can stop and start take screenshots and look at the match from lots of different angles and points of view
halo 3 is a brilliant game online and offline and i very much reccomend you to buy it