Halo 2 > Halo 3 > Halo 3 ODST > Halo Reach > Halo CE
Based on campaigns.
People say that having ODSTs being able to do things they shouldnt be (melee killing brutes, carry turrets, gravity hammers, flip warthogs) is to make gameplay more fun
But think about it. The story in ODST was told with these changes, the story had all of these things in it. Which means that the story cant be canon because it has ODSTS ding these things despite it just being for gameplay
If it were to be canon, it should've been made with out these changes.