if you like the older Halo games you should really look into downloading xbconnect
they always have halo 1 and halo 2 games going
all you do is have the xbconnect program running on your computer which shows you all the games available to join and you click on one and it shows up on your xbox
When I realised Halo 2 was no longer online, I looked into XBConnect briefly. I am going to download it tonight and see how it goes. Thanks!