Halo 2 > Halo 3 > Halo 3 ODST > Halo Reach > Halo CE
Based on campaigns.
Sorry, I know I shouldn't have to make a thread about this, but frankly I think everyone here needs to get the point.
If by any chance you are one of the people worrying that Halo 3 is going to be shut down
Halo 3 CANNOT be shutdown on its own. Halo 3 and all other Xbox 360 games are connected to Live for the Xbox 360. Halo 3 will only be shutdown when Live for the Xbox 360 is shutdown.
Just wanted to get that out there
[Edited on 04.09.2012 6:45 AM PDT]